Mailing List Archive

CIDR FAQ
All follow-ups to cidrd@iepg.org please...

------------------------------------------------------------------------
The CIDR FAQ
Version 1
6 August 1995
------------------------------------------------------------------------
The following document is a collection of Frequently Asked Questions
about CIDR. This document is not meant to be a networking/routing
guide and tutorial. Where appropriate pointers to other documents
of a more general nature have been mentioned.

Updates from a previous version are marked with a '|' in column 1.

If you have any questions you would like added, please send them to
|the editor mentioned below:

Hank Nussbacher (Tel Aviv University and IBM Israel)
hank@vm.tau.ac.il or hank@ibm.net.il

|If you would like to "discuss" items from this FAQ please send
|your mail to cidrd@iepg.org

|This FAQ is being distributed to the following groups and lists:
|alt.internet.services
|alt.internet.access.wanted
|nanog@merit.edu
|inet-access@earth.com
|iap@vma.cc.nd.edu
|local-ir@ripe.net
|cidrd@iepg.org

To retrieve the most up-to-date version of this document:
- anonymous FTP: ftp.ibm.net.il/pub/docs/cidr.faq
------------------------------------------------------------------------

General questions
-----------------

1. What does CIDR stand for?

CIDR stands for Classless Inter-Domain Routing and is documented
in RFC1517/1518/1519/1520. CIDR is an effective method to
stem the tide of IP address allocation as well as routing table
overflow. Without CIDR having been implemented in 1994 & 1995,
the Internet would not be functioning today.

Basically, CIDR eliminates the concept of class A, B, and C
networks and replaces this with a generalized "IP prefix". CIDR
can be used to perform route aggregation in which a single route
can cover the address space of several "old-style" network
numbers and thus replace a lot of old routes. This lessens the
local administrative burden of updating external routing, saves
routing table space in all backbone routers and reduces route
flapping (and thus CPU load) in all backbone routers. CIDR will
also allow delegation of pieces of what used to be called
"network numbers" to customers, and therefore make it possible to
utilize the available address space more efficiently.

See question #6 below for details on "IP prefix"s.

2. What is an ASN?

ASN stands for Autonomous System Number and acts to merge many
networks into a logical domain.

3. What is BGP?

BGP stands for Border Gateway Protocol and is the de-facto
standard for routing between Autonomous Systems in the Internet.
All communications between Internet Service Providers (ISP) is
handled via BGP4 which supports CIDR.

4. Why should I make the effort and convert my routing to be
CIDRized?

The routing tables in the Internet have been growing as fast
as the Internet and the router technology specifically and
computer technology in general has not been able to
keep pace. In December 1990 there were 2190 routes and 2 years
later there were over 8500 routes. In July 1995 there are now
over 29,000 routes and one of the main routers that can handle the
full routing tables are cisco 7000's with 64MB of memory. Routers
with 64MB of memory have the capacity for approximately 60,000
routes after which some routes will just have to be left out of
the global routing tables, and the more likely ones to be left out
are routes covering small pieces of address space.

Without the CIDRization work that has gone on for the past 2 years
the routing tables would be in excess of 65,000 routes. By
CIDRizing you help the Internet reduce the routing overload
as well as increasing the liklihood that in the future your
routes will be carried by all ISPs.

The major benefit of CIDR is to allow for continuous, uninterrupted
growth of the Internet. For a significant percentage of sites
connected to the Internet the value of the Internet increases with
the total number of sites connected to the Internet. Therefore,
taking steps needed to allow for continuous uninterrupted growth
(like CIDRizing, or renumbering) is beneficial to such sites.

The routers today that are available to handle the full routing
table are:

cisco 7000 w/ 32Mb
cisco 4500 w/ 32Mb
IBM 6611' w/ 64Mb (formerly known as ENSS)
BayNetworks ???? w/ 32Mb

5. Can you give an example of a simple CIDR configuration for a
cisco router?

The following example creates 2 aggregates and suppresses
any more specific addresses that may be contained within
those aggregates. The access-list causes only those nets
to be distributed as listed, and not any others that may
exist in the BGP routing tables.

router bgp 64100
no synchronization
aggregate-address 172.16.0.0 255.248.0.0 summary-only
aggregate-address 192.168.50.0 255.255.255.0 summary-only
neighbor 192.168.54.2 remote-as 65000
neighbor 192.168.54.2 distribute-list 12 out
default-metric 70
!
access-list 12 permit 192.168.50.0 0.0.0.255
access-list 12 permit 172.16.0.0 0.7.255.255

An alternate method is via network and route statements:

router bgp 64100
no synchronization
network 172.16.0.0 mask 255.248.0.0
network 192.168.50.0 mask 255.255.255.0
neighbor 192.168.54.2 remote-as 65000
neighbor 192.168.54.2
default-metric 70
ip route 172.16.0.0 255.248.0.0 Null0 254
ip route 192.168.50.0 255.255.255.0 Null0 254

In this case, only those routes explicitly mentioned in "network"
statements will be announced with BGP. For these routes to be
announced, there has to be a corresponding route in the IP
forwarding table, thus the need to create the static routes. The
static routes will also serve as "pull-ups" for the route
advertisements and thus prevent route flapping: these routes will
always be announced with BGP by this router. Note that as long
as more specific routes exist internally in your network, these
will be used in preference to the static "less specific" route
entries (longest prefix matching is being used).

A good rule to follow is to never redistribute IGP learnt routes
directly into BGP, but to rather use network or aggregate-address
statements. And if you must redistribute dynamically learnt IGP
routes into BGP, you MUST use filtering.

The reasons for this advice are several, some of which are:

1) if your IGP is classful (e.g. RIP or IGRP) you will by
default not do any route aggregation
2) if you have an internal stability problem (accidents do
happen), this will be reflected as a "route flap" in the whole
routing system, globally burning CPU cycles better spent on
other things
3) if the IGP -> BGP transition is unrestricted, this can lead to
false routing information escaping from your network
(especially if you do not fully have administrative control
over your IGP)

6. What do all these /16s and /24s mean in my BGP tables?

This refers to the number of bits of the network part of the
IP address. A former class B may appear as 172.50.0.0/16,
which is the same as 256 class C's which can appear as
192.200.0.0/16. A single class C appears as 192.201.1.0/24.
These "things" are often called an "IP prefix", which
consists of an IP address and a mask length. The mask length
specifies the number of leftmost contiguous significant bits in
the corresponding IP address. Thus, an IP prefix with a prefix
length of 15 (denoted /15) covers the address space of 128k IP
addresses, and a /17 covers the address space of 32k IP
addresses.

Here is a table of the more popular CIDR blocks:

# of
former
CIDR class C
block nets
---- ----
/27 1/8
/26 1/4
/25 1/2
/24 1
/23 2
/22 4
/21 8
/20 16
/19 32
/18 64
/17 128
/16 256 = 1 former class B
/15 512
/14 1024
/13 2048

In general, advertising a prefix covering less address space than
a /24 prefix will probably not get into the global routing
tables, and global Internet connectivity is less likely to
happen. Note that for you as an administrator of an AS, it is a
good idea to announce as few prefixes as possible and to utilize
the address space as much as possible.

7. Do I need to carry the full Internet routing table? When would it
be necessary? What routers on the Internet carry full routing
tables and how much memory is needed?

No you do not need to carry the full Internet routing table. If
you are single-homed, meaning you have a single connection to an
ISP, then all you need to do is point a default route to the
ISP and tell your ISP not to send you the full routing table. If
you are multi-homed, you will want to know which nets to route
via connection A and which nets to route via connection B. The
easiest way to do this is to request a partial routing table
from one ISP - with those nets that are closest to them, and default
everything else to the other ISP. This way your routing tables
need not contain the entire Internet universe but only a small
subset.

The closer you get to the hub or nexus of the Internet, the larger
your routing tables need to be. For example, those connected to
public exchange points (like the NAPs, CIX, STIX, LINX, dGIX) in
general, carry full routing tables and run without a default
route.

8. What is there in the Internet to stop me from making a mistake and
announcing via BGP an aggregate that is larger than the nets I am
in charge of?

In principle there is nothing to stop you. The responsibility falls
on both ends of the BGP link - you are responsible to filter what
you announce and the receiving end - if it has its act together -
filters also what it *thinks* it should be hearing from you so as
prevent mistakes on your part. Those sites that do not work with
access lists and filters and just readily accept what is sent to
them are just waiting for a problem to happen.

Filtering can either be done at the IP network level or at the
BGP path (BGP orgin AS) level. See question 20 below for details
on a tool to assist in filtering.

9. Who has to renumber with CIDR ?

Sites that move from one ISP to another, and who had been allocated
| addresses from their original ISP's CIDR block, in all likelihood
| will have to return those addresses as part of the move. The reason
| is to keep the number of prefixes in the global routing system
| within the limits of current technology.

Specific questions
------------------


10. I have a /16 but have registered parts of it as /24s in the RADB.
I now want to CIDRize. The problem is parts of the /16s are
missing and are routed via a different ASN. Can you explain how
more specific routes override more general ones and will I hurt my
routing if I just advertise the /16 and not a bunch of /20s and
/21s?

There are two aspects to the answer:

1) Real (BGP) world: Given there are several AS's sharing addresses
out of a /16 prefix, every AS should advertise exactly those
prefixes which it is really originating. However, if there is one
AS "originating" a significant majority of this address space, the
concerned AS's might agree that this one and only advertises the /16
and all others their more specifics. The more specifics always take
precedence over the less specific.

2) Routing registry: The registry DB, of course, should always
reflect reality. If in the above example the AS's agree on the "big
AS" announcing the /16, the "big AS" should document with the
route-object that it's not really originating the whole aggregate
by using "hole" attributes (see ripe.181, 5. The Route Object).

11. How can I redistribute our IGP routes (IGRP) so that they become
aggregated when sent out via BGP?

It is strongly discouraged to redistribute IGPs into BGP, because
local IGP configuration errors might easily corrupt routing
information of the whole Internet. If, however, you have to do
it anyway, you MUST use strict distribute-lists with explicit
permits (or route-maps) for redistribution. Here is an example
for a Cisco configuration:

router bgp 64100
aggregate-address 192.168.0.0 255.255.192.0 summary-only
aggregate-address 172.16.0.0 255.254.0.0 summary-only
redistribute igrp 64100 route-map origin-AS64100
!
! or:
! redistribute igrp 64100
! distribute-list 10 out igrp 64100
!
route-map origin-AS64100 permit 10
match ip address 10
!
access-list 10 permit 192.168.0.0 0.0.63.0
access-list 10 permit 172.16.0.0
access-list 10 permit 172.17.0.0

This example would generate one route 192.168/18 and one route
172.16/15 if any of the contained networks is in the IGP.

12. I am multihomed to three ISPs and can only CIDRize to two of them
but to the third I need to still announce specific nets. What
damage will this do to my AS?

No damage can be done if the non-CIDR peer does not further
announce your specifics to the global Internet. If your non-CIDR
ISP DOES announce your specifics to the global Internet those
specifics will have preference over the less specifics and
therefore all traffic to you will get routed through the non-CIDR
ISP.

13. I don't want to CIDRize. Can someone do proxy aggregation for me?

Proxy aggregation should only be done with great care and should
be avoided if you are not single-homed ! If you are single-homed
ask your ISP.

14. What routers on the market today don't support CIDR?

???

15. How do I reach other parts of a subnetted old-style network when
I have only partial routing information for that same old-style
network?"

There are actually three ways to solve this particular problem
with Cisco's software. Which of them applies will depend on
what software version is involved:

o Preferred solution: turn on "ip classless" in your routers and
use a default route inside your AS. The "ip classless"
command prevents the existence of a single "subnet" route from
blocking access via the default route to other subnets of the
same old-style network.

o Workaround for 9.1 or later software where the "ip classless"
command is not available: install a "default network route"
like this: "ip route 39.0.0.0 255.0.0.0 next-hop" along the
axis your default route would normally take.

o Workaround for 9.0 or older software: create a "default
subnet route": "ip route 39.x.y.0 next-hop" combined with "ip
default-network 39.x.y.0", otherwise as the 9.1 fix.

Both of the latter solutions rely on static routes, and in the
long run these will be impossible to maintain. In some
topologies the use of static routes can be a problem (e.g. if you
have more than one possible exit point from your AS to choose
from).

Supplemental information
------------------------

The following information is presented as supplemental information
that is related to the CIDRization process.

16. What is the Internet Routing Registry?

The IRR is a way for ASN's to publicize their own intended
routing policies without having to request a change from a
go-between.

The RADB which stands for the Routing Arbiter Data Base, which
is part of the IRR, is part of a joint project between Merit and
ISI. For full details contact:
http://www.ra.net/routing.arbiter/RA/index.html.

The Routing Arbiter is a project of the US National Science
Foundation. As part of that project, it runs a routing
registry database.

That database (the RAdb) forms part of the IRR collection
of databases. The RIPE database is not part of the RAdb
but does participate in the IRR. At present, there are
five entities that contribute to the IRR effort and more
are expected. Today, all the contributing registries use the
RIPE-181 database format.

The Routing Arbiter can be contacted via auto-mail handlers
that accept batch updates via email. An example of a routing
update appears below:

password: xxxxxxxx
*rt: 138.134.0.0/16
*de: NET-IEC
*or: AS378
*mb: AS378-MNT
*ch: hank@aristo.tau.ac.il 950724
*so: RIPE

The *rt: tag identifies the net and the routing policy is based on
*or: tag. An example of a routing policy is presented below:

aut-num: AS378
descr: ILAN
descr: Israeli Academic and Research Network
as-in: from AS1755 100 accept ANY
as-in: from AS174 100 accept ANY
as-in: from AS3339 100 accept AS3339
as-out: to AS1755 announce AS378 AS3339
as-out: to AS174 announce AS378 AS3339
as-out: to AS3339 announce ANY
default: AS174 10
default: AS1755 20
default: AS3339 30
guardian: HANK@vm.biu.ac.il
mnt-by: AS378-MNT
admin-c: Hank Nussbacher
tech-c: Hank Nussbacher
changed: hank@vm.tau.ac.il 950627
source: RIPE

For further details read over ripe-120.ps, ripe-121.ps and
ripe-181.ps (via anonymous ftp from info.ripe.net/ripe/docs).

17. How do I update the registered routing information for my ASN?

You need to submit a "route" object update and perhaps an
"aut-num" object update (see examples above). Route objects
add new nets to your autonomous system (or you can remove nets
from your autonomous system) and the Autonomous-system object
describes the type of routing you wish to have.

18. Which Routing database takes precedence? RIPE? RADB? MCI? Do I
have to update all of them?

ANS uses the following precedence:
ANS, CANET, MCI, RIPE, RADB

If there are two routes (with different origins) within one
database, the changed date is used as a tiebreaker. Else, only
database precedence is used. Thus, if the RADB entry has a more
recent changed date than the RIPE, ANS will use the RIPE entry.

19. How do I check what is in the RA?

The tool to use is whois. A few examples make the command
self explanatory:

whois -h whois.ra.net 128.228.0.0
whois -h whois.ripe.net as378
whois -h whois.canet.ca 142.77.0.0

20. Is there a tool to automatically create route filters based
on IRR information?

rlc is a route list compiler which is a subset of nlc/alc that
allows the generation of route based filters (cisco access-
lists) by extracting the nets belonging to an AS or AS MACRO
from a routing database (i.e. Ripe Routing Database). In
addition, it supports a limited set of functions to generate
AS based filter lists.

rlc is fully classless, and hence supports CIDR routes and
subnets, as well as host routes.

Source: ftp://dxcoms.cern.ch/pub/ripe-routing-wg
Author: Jean-Michel Jouanigot, CERN <jimi@dxcoms.cern.ch>

Contributors:
Christian Panigl - Vienna University, Austria
Bill Manning - ISI
Tony Li - Cisco Systems
Havard Eidnes - SINTEF, Norway
Yakov Rekhter - Cisco Systems
Re: CIDR FAQ [ In reply to ]
Here is a small list for you. Of couse, corrections are most welcome:

Routers that don't support fully support CIDR:
ASCEND Pipeline and MAX products
Telebit Netblazer
Compatible Systems



--
Stan | Academ Consulting Services |internet: sob@academ.com
Olan | For more info on academ, see this |uucp: amdahl!academ!sob
Barber | URL- http://www.academ.com/academ |Opinions expressed are only mine.
Re: CIDR FAQ [ In reply to ]
The cisco 4000-M with 32 M should also support the internet routing table.

Nathan Stratton CEO, NetRail, Inc. Your Gateway to the World!
---------------------------------------------------------------------------
Phone (703)524-4800 NetRail, Inc.
Fax (703)534-5033 2007 N. 15 St. Suite B-5
Email sales@netrail.net Arlington, Va. 22201
WWW http://www.netrail.net/ Access: (703) 524-4802 guest
---------------------------------------------------------------------------
Re: CIDR FAQ [ In reply to ]
> Here is a small list for you. Of couse, corrections are most welcome:
>
> Routers that don't support fully support CIDR:
> ASCEND Pipeline and MAX products
> Telebit Netblazer
> Compatible Systems

Also Livingston IRX and Portmaster. They're RIP-1-only, and hence not
classless.

randy
Re: CIDR FAQ [ In reply to ]
>
>Here is a small list for you. Of couse, corrections are most welcome:
>
>Routers that don't support fully support CIDR:
> ASCEND Pipeline and MAX products
> Telebit Netblazer

Livingston Portmasters, and possibly IRX routers also.
>


--
----------------------------------------------------------------------------
| Jeremy Porter (512)-339-6094 Freeside Communications, Inc. info@fc.net |
| jerry@fc.net (512)-339-4466 (data) P.O. Box 530264 Austin, TX 78753 |
----------------------------------------------------------------------------
Re: CIDR FAQ [ In reply to ]
On Sun, 6 Aug 1995, Jeremy Porter wrote:

> >
> >Here is a small list for you. Of couse, corrections are most welcome:
> >
> >Routers that don't support fully support CIDR:
> > ASCEND Pipeline and MAX products
> > Telebit Netblazer
>
> Livingston Portmasters, and possibly IRX routers also.
> >
>
Yes, add the IRX's to the list. Tho Livingston says they are working on it.

Nathan Stratton CEO, NetRail, Inc. Your Gateway to the World!
---------------------------------------------------------------------------
Phone (703)524-4800 NetRail, Inc.
Fax (703)534-5033 2007 N. 15 St. Suite B-5
Email sales@netrail.net Arlington, Va. 22201
WWW http://www.netrail.net/ Access: (703) 524-4802 guest
---------------------------------------------------------------------------
Re: CIDR FAQ [ In reply to ]
> On Sun, 6 Aug 1995, Jeremy Porter wrote:
>
> > >
> > >Here is a small list for you. Of couse, corrections are most welcome:
> > >
> > >Routers that don't support fully support CIDR:
> > > ASCEND Pipeline and MAX products
> > > Telebit Netblazer
> >
> > Livingston Portmasters, and possibly IRX routers also.
> > >
> >
> Yes, add the IRX's to the list. Tho Livingston says they are working on it.

Since people are throwing in dialup/routing equipment add:

USR Total Control Hubs

-brett
Re: CIDR FAQ [ In reply to ]
Don't you really mean the USR Routing cards for these hubs? You can
put a Cisco AS5100 in them and they route just like a Cisco 2511.

--
Stan | Academ Consulting Services |internet: sob@academ.com
Olan | For more info on academ, see this |uucp: amdahl!academ!sob
Barber | URL- http://www.academ.com/academ |Opinions expressed are only mine.
Re: CIDR FAQ [ In reply to ]
> Don't you really mean the USR Routing cards for these hubs? You can
> put a Cisco AS5100 in them and they route just like a Cisco 2511.

I beleive the reference was to the NetServer cards, which are a
Livingstone based product, and do *not* do CIDR.

BTW Any BSD4.4 based *NIX (NetBSD, FreeBSD, etc) *does* do CIDR.

Regards,
--
Peter Galbavy peter@demon.net
@ Demon Internet phone://44/181/371_3700
http://www.wonderland.org/~peter/
snail://UK/N3_1TT/London/42_Hendon_Lane/Demon_Internet_Ltd/
Re: CIDR FAQ [ In reply to ]
> Livingstone based product, and do *not* do CIDR.
>
> BTW Any BSD4.4 based *NIX (NetBSD, FreeBSD, etc) *does* do CIDR.

Another reason why some people are thinking that workstations and generic
micros sometimes look pretty good as replacements for "real" routers.

You get software that works, full source code, faster CPUs, and fewer
memory limitations. At a cost low enough to get a "free" spare.
Re: CIDR FAQ [ In reply to ]
From: jon@branch.com (Jon Zeeff)
Subject: Re: CIDR FAQ

> BTW Any BSD4.4 based *NIX (NetBSD, FreeBSD, etc) *does* do CIDR.

Another reason why some people are thinking that workstations and generic
micros sometimes look pretty good as replacements for "real" routers.

You get software that works, full source code, faster CPUs, and fewer
memory limitations. At a cost low enough to get a "free" spare.

Look, I really hate to sound like I have sour grapes, but this thread
keeps coming up and I all hear about the PC router issue is a lot of
talk about price and CPUs, but I don't actually hear any operational
experience about them.

PCs have been around for years, and even 4.4+reno/gated boxes have been
around as long as cisco/bgp4 boxes. If they really are such a great value,
why the hell aren't "those evil router vendors" out of business in the
Internet market yet?

Call me thin skinned, but this is really starting to get old.
I would like to personally see the folks who keep extoling the virtues of
roll-your-own solutions either put up or shut up.

Can we kindly return this thread to: "What boxes don't do classless routing?"
Re: CIDR FAQ [ In reply to ]
> Look, I really hate to sound like I have sour grapes, but this thread
> keeps coming up and I all hear about the PC router issue is a lot of
> talk about price and CPUs, but I don't actually hear any operational
> experience about them.

OK. Here we are. We use them in a mission critical environment. For
Ethernet to Ethernet routeing with a full routeing table they are
wonderful. Trying to make them work as fast serial routers is another
matter. But they *do* work.

> PCs have been around for years, and even 4.4+reno/gated boxes have been
> around as long as cisco/bgp4 boxes. If they really are such a great value,
> why the hell aren't "those evil router vendors" out of business in the
> Internet market yet?

There are a large number of reasons, from the technical to the
commercial to the marketing-people-on-steroids reasons.

Reason 1. Special boxes are better. In some cases. Especial for the
non technically competant organisations that don't want to or need to
roll there own. There are of course also Cisco/Bay Networks hackers
too.

Reason 2. "Know one ever got fired for buying Cisco." Remember where that
saying has been adapted from.

Reason 3. Marketing. "We use Cisco/Bay/router-of-the-day in our core network.
We must be profressionals". Hmm.

> Call me thin skinned, but this is really starting to get old.
> I would like to personally see the folks who keep extoling the virtues of
> roll-your-own solutions either put up or shut up.

We have. Thanks. We are very happy using Pentiums running NetBSD as
*core* routers. Three PCI 10/100Mb Ethernet cards. Great stuff.
35,000 dialup SLIP/PPP customers can't be that wrong.

> Can we kindly return this thread to: "What boxes don't do classless routing?"

We did - the CIDR FAQ started out as an ad for Cisco, some of us are
trying to get some balance in this area.

Regards,
--
Peter Galbavy peter@demon.net
@ Demon Internet phone://44/181/371_3700
http://www.wonderland.org/~peter/
snail://UK/N3_1TT/London/42_Hendon_Lane/Demon_Internet_Ltd/
Re: CIDR FAQ [ In reply to ]
On Tue, 15 Aug 1995, Paul Traina wrote:

>
> From: jon@branch.com (Jon Zeeff)
> Subject: Re: CIDR FAQ
>
> > BTW Any BSD4.4 based *NIX (NetBSD, FreeBSD, etc) *does* do CIDR.
>
> Another reason why some people are thinking that workstations and generic
> micros sometimes look pretty good as replacements for "real" routers.
>
> You get software that works, full source code, faster CPUs, and fewer
> memory limitations. At a cost low enough to get a "free" spare.
>
> Look, I really hate to sound like I have sour grapes, but this thread
> keeps coming up and I all hear about the PC router issue is a lot of
> talk about price and CPUs, but I don't actually hear any operational
> experience about them.

Well we are going to use a PC router if all works out for our MAE-East
connection. But we do have a cisco 4500-M if it des not work out.

Nathan Stratton CEO, NetRail, Inc. Your Gateway to the World!
---------------------------------------------------------------------------
Phone (703)524-4800 NetRail, Inc.
Fax (703)534-5033 2007 N. 15 St. Suite B-5
Email sales@netrail.net Arlington, Va. 22201
WWW http://www.netrail.net/ Access: (703) 524-4802 guest
---------------------------------------------------------------------------
Re: CIDR FAQ [ In reply to ]
On Tue, 15 Aug 1995 peter@demon.net wrote:

> > I would like to personally see the folks who keep extoling the virtues of
> > roll-your-own solutions either put up or shut up.
>
> We have. Thanks. We are very happy using Pentiums running NetBSD as
> *core* routers. Three PCI 10/100Mb Ethernet cards. Great stuff.
> 35,000 dialup SLIP/PPP customers can't be that wrong.

Isn't that 600% growth in customers over the past year?

Michael Dillon Voice: +1-604-546-8022
Memra Software Inc. Fax: +1-604-542-4130
http://www.memra.com E-mail: michael@memra.com
Re: CIDR FAQ [ In reply to ]
> > Livingstone based product, and do *not* do CIDR.
> >
> > BTW Any BSD4.4 based *NIX (NetBSD, FreeBSD, etc) *does* do CIDR.
>
> Another reason why some people are thinking that workstations and generic
> micros sometimes look pretty good as replacements for "real" routers.
>
> You get software that works, full source code, faster CPUs, and fewer
> memory limitations. At a cost low enough to get a "free" spare.

Let's excuse the fact that gated consumes more memory than a cisco for the
same amount of routes for a second...

Okay, so let's talk functionality.

Are there HSSI PCI cards available? Can you do SMDS over this card? Frame?
What about a DS3 ATM card, or higher?

I know we can do Ethernet, FDDI, sync, and T1 FR, so that's half of it, but
there are still lot's of reason's to buy Cisco gear.

I'm not excusing the possibility of being able to use PC's, but the additional
management issues of having to manage Unix box's in addition to internal
routing policies, and expansion efforts sounds like a headache. Managing
a network of Cisco's requires a relatively small amount of time, and my staff
and I can concentrate on real problems.

Dave

--
Dave Siegel Director of Engineering, Net99
http://www.webcity.com/ (602)249-1083 24x7 NOC line
http://www.rtd.com/~dsiegel/ (520)318-0696 My Tucson Office
Re: CIDR FAQ [ In reply to ]
At 11:00 AM 8/15/95, Dave Siegel wrote:
>Let's excuse the fact that gated consumes more memory than a cisco for the
>same amount of routes for a second...
>
>Okay, so let's talk functionality.
>
>Are there HSSI PCI cards available? Can you do SMDS over this card? Frame?
>What about a DS3 ATM card, or higher?

And Paul Traina wrote something vaguely similar.

I think you guys are both missing what I think was Jon's original point:
Routers forward packets faster than PCs, but the forwarding function and
the routing protocol function do not have to reside on the same box. You
can add a PC (workstation, whatever) which runs the routing protocol and
stuffs routes into the router. It doesn't have to support the link-layer
du jour. Ethernet will do the job just fine.

As I recall the original discussion was of colocating a router, to forward
packets, with a workstation, to compute routes.

--John
Re: CIDR FAQ [ In reply to ]
> And Paul Traina wrote something vaguely similar.
>
> I think you guys are both missing what I think was Jon's original point:
> Routers forward packets faster than PCs, but the forwarding function and
> the routing protocol function do not have to reside on the same box. You
> can add a PC (workstation, whatever) which runs the routing protocol and
> stuffs routes into the router. It doesn't have to support the link-layer
> du jour. Ethernet will do the job just fine.
>
> As I recall the original discussion was of colocating a router, to forward
> packets, with a workstation, to compute routes.
>

So what would the normal implementation of such a design be? ebgp-multihop
all of your peers into the PC, and then a single peering session the Cisco,
presuming no "next-hop-self" routes?

I can see some amount of value in such a design, if it could be made to work
correctly. Does anybody have the spare equipment to build a lab? (pfeh, yeah,
right)

Dave

--
Dave Siegel Director of Engineering, Net99
http://www.webcity.com/ (602)249-1083 24x7 NOC line
http://www.rtd.com/~dsiegel/ (520)318-0696 My Tucson Office
Re: CIDR FAQ [ In reply to ]
Please remove CIDRD from the CC list for further discussion of the relative
merits of cisco vs. PC routers. This is NOT relavent to the charter of the
CIDR Deployment Working Group.

Thanks,
--Vince (the silent co-chair)
Re: CIDR FAQ [ In reply to ]
On Tue, 15 Aug 1995, Dave Siegel wrote:

> Let's excuse the fact that gated consumes more memory than a cisco for the
> same amount of routes for a second...
>
> Okay, so let's talk functionality.
>
> Are there HSSI PCI cards available? Can you do SMDS over this card? Frame?
> What about a DS3 ATM card, or higher?
>
> I know we can do Ethernet, FDDI, sync, and T1 FR, so that's half of it, but
> there are still lot's of reason's to buy Cisco gear.
>
> I'm not excusing the possibility of being able to use PC's, but the additional
> management issues of having to manage Unix box's in addition to internal
> routing policies, and expansion efforts sounds like a headache. Managing
> a network of Cisco's requires a relatively small amount of time, and my staff
> and I can concentrate on real problems.

Ok, yes you are correct you can't drop a DS3 into the back of a PC, but
why not use a 4500 or 7000 for your ds3's and then use a PC to do the
major BGP4? On a 4500 I only can put in 32 megs or ram. Yes gated will
use more ram for the same number of routes, but I can put 128 meg or more
in a PC.

I think we need to talk about using PC route servers and cisco together
for a solution, the cisco's just can't hold the ram needed.



Nathan Stratton CEO, NetRail, Inc. Your Gateway to the World!
---------------------------------------------------------------------------
Phone (703)524-4800 NetRail, Inc.
Fax (703)534-5033 2007 N. 15 St. Suite B-5
Email sales@netrail.net Arlington, Va. 22201
WWW http://www.netrail.net/ Access: (703) 524-4802 guest
---------------------------------------------------------------------------
Re: CIDR FAQ [ In reply to ]
Ok, yes you are correct you can't drop a DS3 into the back of a PC, but
why not use a 4500 or 7000 for your ds3's and then use a PC to do the
major BGP4? On a 4500 I only can put in 32 megs or ram. Yes gated will
use more ram for the same number of routes, but I can put 128 meg or more
in a PC.

I think we need to talk about using PC route servers and cisco together
for a solution, the cisco's just can't hold the ram needed.

That's why there's the 4500M, and the 7000, and ...

Tony
Re: CIDR FAQ [ In reply to ]
Dave Siegel previously wrote:

>> As I recall the original discussion was of colocating a router, to forward
>> packets, with a workstation, to compute routes.

>So what would the normal implementation of such a design be? ebgp-multihop
>all of your peers into the PC, and then a single peering session the Cisco,
>presuming no "next-hop-self" routes?

No. Colocated BGP4 "proxies" (I'm still not sure what to call these,
anyone?) would peer via EBGP with other ASes BGP4 "proxies" on the same
net. The next_hop BGP4 attribute on all routes exchanged would be that
of the routers on the high speed interconnect, not of the "proxies."
ASes that do not implement this would still peer via EBGP
router-to-router as usual and would not see the "proxies;" eventually
everyone would move towards having "proxies" or else router vendors
would beef up their products, either way, we're all happy.

>I can see some amount of value in such a design, if it could be made to work
>correctly. Does anybody have the spare equipment to build a lab? (pfeh, yeah,
>right)

It would work (see the comment on the next_hop BGP4 attribute above).

I'm sure there are folk out there that would be willing to experiment,
all you need is for two ASes to try it at some exchange (and permission
by the exchange to run the necessary ethernet).

>Dave
>
>--
>Dave Siegel Director of Engineering, Net99
>http://www.webcity.com/ (602)249-1083 24x7 NOC line
>http://www.rtd.com/~dsiegel/ (520)318-0696 My Tucson Office
>


Nick
Re: CIDR FAQ [ In reply to ]
> >So what would the normal implementation of such a design be? ebgp-multihop
> >all of your peers into the PC, and then a single peering session the Cisco,
> >presuming no "next-hop-self" routes?
>
> No. Colocated BGP4 "proxies" (I'm still not sure what to call these,
> anyone?) would peer via EBGP with other ASes BGP4 "proxies" on the same
> net. The next_hop BGP4 attribute on all routes exchanged would be that
> of the routers on the high speed interconnect, not of the "proxies."
> ASes that do not implement this would still peer via EBGP
> router-to-router as usual and would not see the "proxies;" eventually
> everyone would move towards having "proxies" or else router vendors
> would beef up their products, either way, we're all happy.
>
>
> Nick
>

This is very similar to the existing RA route server design. If you want
to play with this, then pick up the RS code and try it out. Its a lot
closer than the gated base is for doing this kind of "toying around".

--bill
Re: CIDR FAQ [ In reply to ]
bmanning@ISI.EDU previously wrote:

>> No. Colocated BGP4 "proxies" (I'm still not sure what to call these,
>> anyone?) would peer via EBGP with other ASes BGP4 "proxies" on the same
>> net. The next_hop BGP4 attribute on all routes exchanged would be that
>> of the routers on the high speed interconnect, not of the "proxies."
>> ASes that do not implement this would still peer via EBGP
>> router-to-router as usual and would not see the "proxies;" eventually
>> everyone would move towards having "proxies" or else router vendors
>> would beef up their products, either way, we're all happy.


>> Nick


>This is very similar to the existing RA route server design. If you want
>to play with this, then pick up the RS code and try it out. Its a lot
>closer than the gated base is for doing this kind of "toying around".

Indeed. In fact, it is the same idea as that of an RS to some point: the
routers on the high speed interconnect use a single BGP4 neighbor to
hear and announce routes at the XP. The only difference is that a single
organization would run a given RS, but with "proxies" everyone is in
full control of their AS. A single RS is nicer in some ways though: it
can make a lot of safety checks against the routing policy database it
needs to run, but only if the database reflects reality and changes to
it are monitored. It's a question of what architecture will be prefered
in the end by NAPs and their members; I'd like to give the RA RS a good
chance.

I was thinking of using the RS code to experiment with implementing some
of the weird features I've mentioned in other posts.

>--bill
>

Nick
Re: CIDR FAQ [ In reply to ]
Tony Li previously wrote:

> The original post was about making time at the Pittsburg NANOG meeting
> to talk about solutions to the problem of some exchange routers seeing
> tens of thousands (even 100x) paths. The size of a full-Internet route
> table is growing (albeit more slowly than it used to), the number of
> ASes meeting at the various NAPs and MAEs is increasing, etc. Will the
> number of paths heard by some routers at the XPs ever be so large that
> they don't fit in the 7000 or 4500m's 64MB of RAM? Possibly (IMHO,
> likely). What then? Use lots of filtering to keep the number of paths
> heard down and lose flexibility?

>Then I ask you to sign a nondisclosure agreement. ;-)

Oh, then the whole argument is for naught. :)

>We've actually been very good (some say too good) about adding
>features.

Yes, Cisco is very good about adding software features and even about
allowing its customers to beta test software.

>Tony
>

Nick
Re: CIDR FAQ [ In reply to ]
>Then I ask you to sign a nondisclosure agreement. ;-)

Oh, then the whole argument is for naught. :)

Correct. Please fixate on the long term growth rate. That is key.
Unless you want your PC to have Gigabytes of RAM.

Tony

1 2 3 4 5  View All