Re: Need BGP Update-Groups explanation

rlortiz · ‎03-30-2005

We are confused by the output of the show ip bpg commands on a 12.0(29)S router and other IOS version routers like a 12.1(22)E1 router. (I have removed most of the ip addresses for security reasons)

router1#sh ip bgp xx.xx.xx.xx

BGP routing table entry for xx.xx.xx.xx/32, version 465794

Paths: (2 available, best #1)

Advertised to update-groups:

1 2 3 4 5 6 7

14496

xx.xx.xx.xx from xx.xx.xx.xx (192.25.199.9)

Origin IGP, metric 5, localpref 120, valid, external, best

Community: 9827:120

14496

xx.xx.xx.xx (metric 510) from 192.46.77.190 (192.46.77.190)

Origin IGP, metric 5, localpref 120, valid, internal

Community: 9827:120

Cisco Internetwork Operating System Software

IOS (tm) RSP Software (RSP-PV-M), Version 12.0(29)S, RELEASE SOFTWARE (fc1)

Technical Support: http://www.cisco.com/techsupport

Compiled Wed 04-Aug-04 16:01 by kellmill

Image text-base: 0x400110A8, data-base: 0x41430000

What is this notation ( 1 - 7 ) of update-groups and how to read it ?

As compared to a similar command on router2:

router2#sh ip bgp xx.xx.xx.xx

BGP routing table entry for 192.46.77.1/32, version 3788128

Paths: (2 available, best #1, table Default-IP-Routing-Table)

Advertised to peer-groups:

BB->Site HRR->client-lite HRR->EAR

Advertised to non peer-group peers:

xx.xx.xx.xx xx.xx.xx.xx

9827

xx.xx.xx.xx (metric 400) from 192.25.199.9 (192.25.199.9)

Origin IGP, metric 5, localpref 120, valid, internal, best

Community: 14496:120

9827

xx.xx.xx.xx from xx.xx.xx.xx (192.46.77.190)

Origin IGP, metric 320, localpref 120, valid, external

Community: 14496:120

router2#sh hard

Cisco Internetwork Operating System Software

IOS (tm) c6sup2_rp Software (c6sup2_rp-PSV-M), Version 12.1(22)E1, EARLY DEPLOYM

ENT RELEASE SOFTWARE (fc1)

Technical Support: http://www.cisco.com/techsupport

Compiled Sat 17-Apr-04 07:01 by pwade

Image text-base: 0x40008F90, data-base: 0x41878000

Harold Ritter · ‎03-30-2005

BGP update-groups (AKA dynamic update peer-groups) is a BGP optimization that allows the router to process an update once and send it to a group of neighbor that share a common outbound policy. This is done without additional configuration contrary to peer-groups.

To see which neighbors are member of a given update-group, use the "show ip bgp update-group " command as follow:

r1#sh ip bgp update-group 1

BGP version 4 update-group 1, internal, Address Family: IPv4 Unicast

BGP Update version : 6, messages 0/0

Update messages formatted 4, replicated 0

Number of NLRIs in the update sent: max 0, min 0

Minimum time between advertisement runs is 5 seconds

Has 1 member (* indicates the members currently being sent updates):

2.2.2.2

For more information on this feature, refer to the following URL:

http://www.cisco.com/en/US/partner/products/sw/iosswrel/ps1829/products_feature_guide09186a008012ed14.html

Hope this helps,

Harold Ritter
Sr Technical Leader
CCIE 4168 (R&S, SP)
harold@cisco.com
México móvil: +52 1 55 8312 4915
Cisco México
Paseo de la Reforma 222
Piso 19
Cuauhtémoc, Juárez
Ciudad de México, 06600
México

rlortiz · ‎03-31-2005

hritter,

Thanks for the information. So,from what you stated there is no need for any BGP configuration in order

to benefit from that new feature. In that regard, what is the meaning of the 7 update groups in the sngbbr1 case. Does it indicate that 7 groups get build and each need to be displayed by using the sh ip bgp update-group xx ?

BGP routing table entry for 192.25.155.9/32, version 465794

Paths: (2 available, best #1)

Advertised to update-groups:

1 2 3 4 5 6 7