Re: BGP Convergence

Next hop tracking will greatly speed things up ...

What about BFD? Platform support is sketchy ... but on most of the software
platforms you can probably run this. You can also tune the timers some but
... this is not always preferred since it can be taxing on the CPU. If you
can run BFD, this is better than changing the timers. Is your question
related to production or lab?

HTH,

Andrew Lee Lissitz

On Tue, Jun 30, 2009 at 1:59 PM, kaushalccie patel <kaushalccie_at_gmail.com>wrote:

> I went through both options, And found following diff..
>
>
> http://www.cisco.com/en/US/partner/docs/ios/iproute/command/reference/irp_bgp3.html#wp1013842
> *neighbor** **ip-address** *fall-over [*bfd* | *route-map* *map-name*]
> monitor the peering session of a specified neighbor for adjacency changes
> and to deactivate the peering session,
> Adjacency changes are detected, and terminated peering sessions are
> deactivated in between the default or configured BGP scanning interval.
>
> By default, the BGP scanner is used to poll the RIB for this information
> every 60 seconds. During the 60 second time period between scan cycles,
> Interior Gateway Protocol (IGP) instability or other network failures can
> cause black holes and routing loops to temporarily form.
>
>
> *bgp fast-external-fallover *
> for BGP peering sessions with directly connected external peers
> The session is immediately reset if link goes down. Only directly connected
> peering sessions are supported.
>
>
> http://www.cisco.com/en/US/partner/docs/ios/iproute/command/reference/irp_bgp2.html#wp1015842
> *ip bgp fast-external-fallover* [*permit *| *deny*]
> per-interface fast external fallover
> overriding the global configuration
>
> If we compare both the option,
> In Terms of Faster Detection - Link Failures will be detected first and
> then
> BGP Session failure
> But - bgp fast-external-fallover - supports only directly connected
> neighbors.
>
> HTH
> -Kaushal
>
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-- 
Andrew Lee Lissitz
all.from.nj_at_gmail.com
Blogs and organic groups at http://www.ccie.net