By default, BGP updates are sent on a neighbor to neighbor basis and the result more CPU resources being used, also by implementing non-default settings for example performing filtering using prefix lists, route map, or filter list to those neighbors, even more CPU resources are consume.





When, many neighbors are having similar configuration parameters. Cisco IOS allows us to create logical group those similar neighbors into a BGP peer group then you apply your non-default BGP configuration to those parameters to each neighbor individually. Actually a single router can have multiple peer groups, each representing a separate set of parameters. The result less CPU resources required. Remember router still sends out individual BGP updates to each of its neighbors. It does require based on BGP characteristics of establishing a TCP session with each neighbor.







Inshort: BGP peer group means applying same policies to multiple neighbors.It's useful when many neighbors have the same configuration parameter. updates are generated once per peer group.

















lets see the configurations.

Topology:





Goal:

configure the topology as per the diagram and its interfaces.

configure eigrp 100 all the routers to ensure the reachability between the loopbacks.

configure loopback 0 to establishing peering, configure peer group name cisco.

configure authentication and make sure all the peer should use same password.(in our topology we use internetworks)

configure BGP version 4 and advertise LAN interfaces only.





R1#show ip interface brief

Interface IP-Address OK? Method Status Protocol FastEthernet0/0 10.1.1.1 YES manual up up Serial3/0 1.1.1.1 YES manual up up Serial3/3 4.1.1.2 YES manual up up Loopback0 11.0.0.1 YES manual up up Loopback1 11.0.1.1 YES manual up up Loopback2 11.0.2.1 YES manual up up Loopback3 11.0.3.1 YES manual up up



























R2(config)#router eigrp 100 R2(config-router)#network 20.0.0.0 R2(config-router)#network 2.0.0.0 R2(config-router)#network 1.0.0.0 R2(config-router)#network 12.0.0.0 R2(config-router)#no auto-summary R2(config-router)#end







R3(config)#router eigrp 100 R3(config-router)#network 13.0.0.0 R3(config-router)#network 2.0.0.0 R3(config-router)#network 3.0.0.0 R3(config-router)#network 30.0.0.0 R3(config-router)#no auto-summary R3(config-router)#end



R4(config)#router eigrp 100

R4(config-router)#network 4.0.0.0 R4(config-router)#network 4.0.0.0 R4(config-router)#network 40.0.0.0 R4(config-router)#network 14.0.0.0 R4(config-router)#network 3.0.0.0 R4(config-router)#end























R3(config)#router bgp 501







R4(config)#router bgp 501 R4(config-router)#neighbor cisco peer-group R4(config-router)#neighbor cisco remote-as 501 R4(config-router)#neighbor cisco update-source loopback 0 R4(config-router)#neighbor cisco version 4 R4(config-router)#neighbor cisco password internetworks R4(config-router)#neighbor 12.0.0.1 peer-group cisco R4(config-router)#neighbor 13.0.0.1 peer-group cisco R4(config-router)#neighbor 11.0.0.1 peer-group cisco R4(config-router)#network 40.0.0.0 R4(config-router)#no auto-summary R4(config-router)#no synchronization R4(config-router)#end













R2#show ip bgp summary BGP router identifier 12.0.3.1, local AS number 501 BGP table version is 9, main routing table version 9 4 network entries using 576 bytes of memory 4 path entries using 320 bytes of memory 2/2 BGP path/bestpath attribute entries using 272 bytes of memory 0 BGP route-map cache entries using 0 bytes of memory 0 BGP filter-list cache entries using 0 bytes of memory BGP using 1168 total bytes of memory BGP activity 4/0 prefixes, 6/2 paths, scan interval 60 secs



Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd 11.0.0.1 4 501 8 8 9 0 0 00:01:23 1 13.0.0.1 4 501 8 8 9 0 0 00:01:26 1 14.0.0.1 4 501 8 6 9 0 0 00:01:32 1







R3#show ip bgp summary BGP router identifier 13.0.3.1, local AS number 501 BGP table version is 7, main routing table version 7 4 network entries using 576 bytes of memory 4 path entries using 320 bytes of memory 2/2 BGP path/bestpath attribute entries using 272 bytes of memory 0 BGP route-map cache entries using 0 bytes of memory 0 BGP filter-list cache entries using 0 bytes of memory BGP using 1168 total bytes of memory BGP activity 5/1 prefixes, 5/1 paths, scan interval 60 secs



Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd 11.0.0.1 4 501 21 19 7 0 0 00:11:15 1 12.0.0.1 4 501 9 9 7 0 0 00:02:00 1 14.0.0.1 4 501 9 11 7 0 0 00:03:56 1







R4#show ip bgp summary BGP router identifier 14.0.3.1, local AS number 501 BGP table version is 5, main routing table version 5 4 network entries using 576 bytes of memory 4 path entries using 320 bytes of memory 2/2 BGP path/bestpath attribute entries using 272 bytes of memory 0 BGP route-map cache entries using 0 bytes of memory 0 BGP filter-list cache entries using 0 bytes of memory BGP using 1168 total bytes of memory BGP activity 4/0 prefixes, 4/0 paths, scan interval 60 secs



Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd 11.0.0.1 4 501 11 12 5 0 0 00:04:24 1 12.0.0.1 4 501 7 9 5 0 0 00:02:40 1 13.0.0.1 4 501 11 9 5 0 0 00:04:29 1







R1#show ip bgp BGP table version is 7, local router ID is 11.0.3.1 Status codes: s suppressed, d damped, h history, * valid, > best, i - internal, r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter, x best-external, a additional-path, c RIB-compressed, Origin codes: i - IGP, e - EGP, ? - incomplete RPKI validation codes: V valid, I invalid, N Not found



Network Next Hop Metric LocPrf Weight Path *> 10.0.0.0 0.0.0.0 0 32768 i r>i 20.0.0.0 12.0.0.1 0 100 0 i r>i 30.0.0.0 13.0.0.1 0 100 0 i r>i 40.0.0.0 14.0.0.1 0 100 0 i







R3#show ip bgp BGP table version is 7, local router ID is 13.0.3.1 Status codes: s suppressed, d damped, h history, * valid, > best, i - internal, r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter, x best-external, a additional-path, c RIB-compressed, Origin codes: i - IGP, e - EGP, ? - incomplete RPKI validation codes: V valid, I invalid, N Not found

Network Next Hop Metric LocPrf Weight Path r>i 10.0.0.0 11.0.0.1 0 100 0 i r>i 20.0.0.0 12.0.0.1 0 100 0 i *> 30.0.0.0 0.0.0.0 0 32768 i r>i 40.0.0.0 14.0.0.1 0 100 0 i

R1#show processes cpu history







11111 111122222111111111111111333330000044444666663333311111222225 100 90 80 70 60 50 40 30 20 10 ***** ***** 0....5....1....1....2....2....3....3....4....4....5....5....6 0 5 0 5 0 5 0 5 0 5 0 CPU% per second (last 60 seconds)









1 1 3 024436222553333343433323324419263322223223312322262433222322 100 90 80 70 60 50 40 30 * 20 * 10 * * ** ** * * # 0....5....1....1....2....2....3....3....4....4....5....5....6 0 5 0 5 0 5 0 5 0 5 0 CPU% per minute (last 60 minutes) * = maximum CPU% # = average CPU%









31 42 100 90 80 70 60 50 40 30 * 20 * 10 ** 0....5....1....1....2....2....3....3....4....4....5....5....6....6....7.. 0 5 0 5 0 5 0 5 0 5 0 5 0 CPU% per hour (last 72 hours) * = maximum CPU% # = average CPU%



















R2#show ip interface briefInterface IP-Address OK? Method Status ProtocolFastEthernet0/0 20.1.1.1 YES manual up upSerial3/0 1.1.1.2 YES manual up upSerial3/1 2.1.1.1 YES manual up upLoopback0 12.0.0.1 YES manual up upLoopback1 12.0.1.1 YES manual up upLoopback2 12.0.2.1 YES manual up upLoopback3 12.0.3.1 YES manual up upR3#show ip interface briefInterface IP-Address OK? Method Status ProtocolFastEthernet0/0 30.1.1.1 YES manual up upSerial3/1 2.1.1.2 YES manual up upSerial3/2 3.1.1.1 YES manual up upLoopback0 13.0.0.1 YES manual up upLoopback1 13.0.1.1 YES manual up upLoopback2 13.0.2.1 YES manual up upLoopback3 13.0.3.1 YES manual up upR4#show ip interface briefInterface IP-Address OK? Method Status ProtocolFastEthernet0/0 40.1.1.1 YES manual up upSerial3/2 3.1.1.2 YES manual up upSerial3/3 4.1.1.1 YES manual up upLoopback0 14.0.0.1 YES manual up upLoopback1 14.0.1.1 YES manual up upLoopback2 14.0.2.1 YES manual up upLoopback3 14.0.3.1 YES manual up upR1(config)#router eigrp 100R1(config-router)#network 10.0.0.0R1(config-router)#network 1.0.0.0R1(config-router)#network 4.0.0.0R1(config-router)#network 11.0.0.0R1(config-router)#no auto-summaryR1(config-router)#endR1(config)#router bgp 501R1(config-router)#neighbor cisco peer-groupR1(config-router)#neighbor cisco remote-as 501R1(config-router)#neighbor cisco update-source loopback 0R1(config-router)#neighbor cisco version 4R1(config-router)#neighbor cisco password internetworksR1(config-router)#neighbor 12.0.0.1 peer-group ciscoR1(config-router)#neighbor 13.0.0.1 peer-group ciscoR1(config-router)#neighbor 14.0.0.1 peer-group ciscoR1(config-router)#network 10.0.0.0R1(config-router)#no auto-summaryR1(config-router)#no synchronizationR1(config-router)#endR2(config)#router bgp 501R2(config-router)#neighbor cisco peer-groupR2(config-router)#neighbor cisco remote-as 501R2(config-router)#neighbor cisco update-source loopback 0R2(config-router)#neighbor cisco version 4R2(config-router)#neighbor cisco password internetworksR2(config-router)#neighbor 11.0.0.1 peer-group ciscoR2(config-router)#neighbor 13.0.0.1 peer-group ciscoR2(config-router)#neighbor 14.0.0.1 peer-group ciscoR2(config-router)#network 20.0.0.0R2(config-router)#no auto-summaryR2(config-router)#no synchronizationR2(config-router)#endR3(config-router)#neighbor cisco peer-groupR3(config-router)#neighbor cisco remote-as 501R3(config-router)#neighbor cisco update-source loopback 0R3(config-router)#neighbor cisco version 4R3(config-router)#neighbor cisco password internetworksR3(config-router)#neighbor 12.0.0.1 peer-group ciscoR3(config-router)#neighbor 11.0.0.1 peer-group ciscoR3(config-router)#neighbor 14.0.0.1 peer-group ciscoR3(config-router)#network 30.0.0.0R3(config-router)#no auto-summaryR3(config-router)#no synchronizationR3(config-router)#endR1#show ip bgp summaryBGP router identifier 11.0.3.1, local AS number 501BGP table version is 7, main routing table version 74 network entries using 576 bytes of memory4 path entries using 320 bytes of memory2/2 BGP path/bestpath attribute entries using 272 bytes of memory0 BGP route-map cache entries using 0 bytes of memory0 BGP filter-list cache entries using 0 bytes of memoryBGP using 1168 total bytes of memoryBGP activity 5/1 prefixes, 5/1 paths, scan interval 60 secsNeighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd12.0.0.1 4 501 7 7 7 0 0 00:00:44 113.0.0.1 4 501 17 20 7 0 0 00:10:02 114.0.0.1 4 501 9 9 7 0 0 00:02:37 1