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about bgp graceful-restart and soft-reconfiguration

ariela
Level 4
Level 4

Hi folks,

what the difference between bgp graceful-restart and peer soft-reconfiguration? The first is only for dual route processors systems, or maybe the behavior is quite different?

Thanks for your support

Regards

Andrea

1 Accepted Solution

Accepted Solutions

mheusinger
Level 10
Level 10

Hi,

soft-reconfiguration will store all BGP updates from a neighbor in memory, i.e. you have an exact copy of the updates BEFORE your filters. Thus "clear ip bgp soft in" will allow you to apply modified filters without neighbor involvement. Your router takes the locally stored copy of the updates and processes them again.

Once your route processor dies, however, all BGP sessions die. Once the session is terminated also the "soft" copy in memory is removed and the forwarding table is cleared.

So bgp graceful-restart addresses this problem: one RP dies and a second one is present to take over. The line cards will keep the forwarding table though the BGP session is gone until BGP establishes full connecivity again. The result is: your users will have less disruption (if any).

Hope this helps! Please rate all posts.

Regards, Martin

View solution in original post

3 Replies 3

mheusinger
Level 10
Level 10

Hi,

soft-reconfiguration will store all BGP updates from a neighbor in memory, i.e. you have an exact copy of the updates BEFORE your filters. Thus "clear ip bgp soft in" will allow you to apply modified filters without neighbor involvement. Your router takes the locally stored copy of the updates and processes them again.

Once your route processor dies, however, all BGP sessions die. Once the session is terminated also the "soft" copy in memory is removed and the forwarding table is cleared.

So bgp graceful-restart addresses this problem: one RP dies and a second one is present to take over. The line cards will keep the forwarding table though the BGP session is gone until BGP establishes full connecivity again. The result is: your users will have less disruption (if any).

Hope this helps! Please rate all posts.

Regards, Martin

mscott21
Level 1
Level 1

This is helpful but then the question becomes why use soft-reconfiguration at all when graceful-restart appears to be the best option

 

make new post it better

MHM

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