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Community Member

bgp slow peer for PE/RR


Recently came into one concenpt, " bgp slow peer " for PE or RR

In our network we have 2 no RR & all RR are having ibgp with PE router

So, in that above case the feature will give any faster convergence

What are the pros/cons of this feature


Cisco Employee

bgp slow peer for PE/RR


Slow peer in BGP is a feature that works in conjunction with BGP update groups. Update groups are formed automatically in BGP for iBGP and eBGP neighbors. Neighbors with the same outbound policy end up in the same update group. The BGP update is then created once and replicate to all other neighbors in the update group. This is more efficient than creating one BGP update for each neighbor seperately. Slow peer feature will detect if a peer is slowing in processing received BGP messages. That peer will be moved out of the update group. The reason is that one slow peer can slow down the whole update group, which has potentially many neighbors. So, the more neighbors in an update group, the effect will be greater of the slow peer feature. In the end, slow peer feature makes convergence go faster, if there is one or more slow BGP peer. This feature can benefit BGP everywhere, on RR, PE or any BGP router. Remember, the more BGP neighbors with the same outbound policy, the greater the effect can be. Likely, the RRs do not have different or any outbound policy on the iBGP sessions, so there it can be very useful. Also, it might benefit the PE-CE sessions, if you have more than one per VRF at least.



Cisco Employee

Hello Luc,

Hello Luc,

How slow peer feature check that particular peer is slow and then it moves to diff update-group.

I am asking because even after enabling slow peer feature on RR ,it is moving few peers to diff update-group and few left as slow in main update-group. What I can check to make all slow peer to diff update-group using this feature. 


address-family vpnv4
  bgp slow-peer detection
    neighbor PE_Routers slow-peer detection threshold 120
  neighbor PE_Routers slow-peer split-update-group dynamic permanent


NOD-MPL-RR-RTR-37-4#sh ip bgp vpnv4 al summary | i SE  4         9730 1840013 312926829        1    0 2008 15w0d        1834 (SE) >>>>>Not moved   4         9730 1730873 3086363683        1    0    0 1y48w         498 (SE)

NOD-MPL-RR-RTR-37-4#sh ip bgp vpnv4 all summary slow

BGP activity 854632271/853836769 prefixes, 3016637633/3015125149 paths, scan interval 60 secs

Neighbor        V           AS MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down  State/PfxRcd   4         9730  177229 285261102 727051009    0    0 14w5d         305>>>>these peer have moved  4         9730  148652 244116884 727051009    0    0 12w1d         218




Community Member

bgp slow peer for PE/RR

Hi Shubhojit,

Apart to what Luc mentioned on the slow peers it is always good to reinforce the root cause as to what is causing the slow peers..

1. Reinforcing any mis-behaving links which ic creating flaps

2. Adjusting TCP MSS sizes

3. Checking if the right Hardware is being used,

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