Internet Edge Router replacement - IPv6 route table sizeconsiderations

George Bonser gbonser at seven.com
Wed Mar 9 01:19:52 CST 2011


> -----Original Message-----
> From: Frank Bulk [mailto:frnkblk at iname.com]
> Sent: Tuesday, March 08, 2011 10:13 PM
> To: George Bonser; nanog at nanog.org
> Subject: RE: Internet Edge Router replacement - IPv6 route table
> sizeconsiderations
> 
> That's 1M IPv4 routes, IIRC.  Put IPv6 into the mix and that 1M
quickly
> shrinks.
> 
> Frank
> 

Yes, you have two choices with the Brocade gear.  You can have it set to
install the /64 prefix in the table making a v6 route 2x as expensive as
a v4 route (default behavior) or you can have it use the entire 128 bit
destination where it becomes 4x more expensive.

The ipv4-ipv6-2 CAM profile in 5.1 gives 768K v4 routes and 64k v6
routes which should be good for quite a while.  That is provided you
aren't using MPLS VPNs. If you are, the best you can get using static
CAM profiles is multi-service-2 which gives you 384K v4 and 128K v6.
But you can put the thing in dynamic cam mode where unused entries can
be aged out saving resources for routes you never really talk to:

Dynamic mode - In the dynamic mode, routes are entered into the CAM
dynamically using a
flow-based scheme, where routes are only added to the CAM as they are
required. Once routes
are added to the CAM, they can be aged-out when they are not in use.
Because this mode
conserves CAM, it is useful for situations where CAM resources are
stressed or limited.

Static mode - In the static mode, routes are entered into the CAM
whenever they are
discovered. Routes are not aged once routes are added to the CAM and can
be aged-out when
they are not in use.

The default behavior is static mode.  I use dynamic mode on dual-stack
gear at the moment with the ipv4-ipv6-2 CAM profile.





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