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Re: Router upgrade for small colo provider
From: "Andrew - Supernews" <andrew () supernews net>
Date: Wed, 25 Jan 2006 02:05:59 +0000


"josh" == josh harrington <jharington68 () hotmail com> writes:

 josh> [option #3 - Cisco 6509 switch'router' w/MSFC2]
 [...]

 josh> - 'not a router' as some would say [though this one is as good
 josh> as it gets for a switch with router ability built in, so i read
 josh> at least]

It routes packets, therefore it is a router :-)

Seriously, the people who call it "not a router" are talking through
their hats.

 josh> - bgp4 support appears limited in previous versions, but the
 josh> MSFC2 processor supposedly can handle (2) bgp4 sessions
 josh> properly [makes me nervous]

I have some of these running with combinations ranging from 5
full-routes sessions + iBGP through to 2 full + iBGP + 70+ peers.  You
don't need to be nervous about the MSFC2's ability to do BGP (though
for serious work you do want the maximum memory in both the MSFC2
_and_ the Sup2 (512M and 256M respectively) - the 256M on the Sup2 is
_important_ if you're going to have full routes).

 josh> - no support for anything but 100mbit, or gigE links, wont work
 josh> with t3, or oc3 lines

I understand there are modules for other interface types. No idea how
easy they are to get hold of; we only use gigE.

 josh> - 'all eggs in 1 basket' theory, if it breaks you loose all
 josh> your ether switches! [at least with separate routers/switches i
 josh> can swap in an old 7206 router spare and get back online fast
 josh> in a worst case scenario.

We solve this by having multiple routers...

Other negative factors you didn't list:

  - PFC2 has a hardware forwarding table limit of about 256k prefixes
    (of which I think some are reserved). uRPF cuts that in half.
    Current routing table size is ~176k prefixes... so no uRPF
    possible with full routes, and the total routing table size may
    become an issue.

  - PFC2 doesn't support IPv6. At all. I don't know if any IOS versions
    available for the 65xx support IPv6 in software, but...:

  - MSFC2 has relatively limited capacity for forwarding traffic in
    software.  This normally isn't a problem, but it means you have to
    be careful not to do things (like trying to log traffic in ACLs)
    that result in your main traffic flows being punted to the MSFC.

There are lots of other advantages besides the ones you mentioned,
though.

-- 
Andrew, Supernews
http://www.supernews.com


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