on 03-29-2012 06:44 AM
This document explains behaviour of Cisco routers running IOS-XR when configuring soft-reconfiguration Inbound
Possible scenarios:
1. - When the BGP neighbour is not route refresh capable:
1.1 No soft-reconfiguration configured
1.2 Soft-reconfiguration configured
1.3 Soft-reconfiguration always configured
2. - When the BGP neighbour is route refresh capable:
2.1 No soft-reconfiguration configured
2.2 Soft-reconfiguration configured
2.3 Soft-reconfiguration always configured
Descriptions and outputs
1. - No route refresh capability:
1.1 No soft-reconfiguration configured
#sh bgp vrf [vrf_name] neighbors [neighbour_address] detail
BGP neighbor is [neighbour_address], vrf [vrf_name]
Remote AS ###, local AS ###, external link
<snip>
Neighbor capabilities: Adv Rcvd
Route refresh: Yes No
4-byte AS: Yes No
Address family IPv4 Unicast: Yes Yes
<snip>
#show bgp vrf [vrf_name] neighbors [neighbour_address] received routes
% The 'show bgp neighbor received routes' command is only available when inbound soft reconfiguration is active.
To activate inbound soft reconfiguration, use the 'soft-reconfiguration inbound' command.
If the neighbor supports route-refresh, the 'always' option to the command must also be specified.
1.2 Soft-reconfiguration configured
#sh bgp vrf [vrf_name] neighbors [neighbour_address] detail
BGP neighbor is [neighbour_address], vrf GRX
Remote AS ###, local AS ###, external link
<snip>
Neighbor capabilities: Adv Rcvd
Route refresh: Yes No
4-byte AS: Yes No
Address family IPv4 Unicast: Yes Yes
<snip>
#show bgp vrf [vrf_name] neighbors [neighbour_address] received routes
BGP VRF [vrf_name], state: Active
BGP Route Distinguisher: [Route Distinguisher number]
VRF ID: [vrf_id]
BGP router identifier [router-id], local AS number [AS-number]
Non-stop routing is enabled
BGP table state: Active
Table ID: #####
BGP main routing table version ###
BGP NSR Initial initsync version 8 (Reached)
Dampening enabled
Status codes: s suppressed, d damped, h history, * valid, > best
i - internal, r RIB-failure, S stale
Origin codes: i - IGP, e - EGP, ? – incomplete
Network Next Hop Metric LocPrf Weight Path
Route Distinguisher: [RD_number] (default for vrf [vrf_name])
* 1.1.2.0/25 192.168.100.1 0 0 6774 ?
s 1.1.1.0/24 192.168.100.1 0 0 6774 ?
* 192.168.100.0/24 192.168.100.1 0 0 6774 ?
* 192.168.101.0/24 192.168.100.1 0 0 6774 ?
Processed 4 prefixes, 4 paths
1.3 Soft-reconfiguration always configured
#sh bgp vrf [vrf_name] neighbors [neighbour_address] detail
BGP neighbor is [neighbour_address], vrf GRX
Remote AS ###, local AS ###, external link
<snip>
Neighbor capabilities: Adv Rcvd
Route refresh: Yes No
4-byte AS: Yes No
Address family IPv4 Unicast: Yes Yes
<snip>
#show bgp vrf [vrf_name] neighbors [neighbour_address] received routes
BGP VRF [vrf_name], state: Active
BGP Route Distinguisher: [Route Distinguisher number]
VRF ID: [vrf_id]
BGP router identifier [router-id], local AS number [AS-number]
Non-stop routing is enabled
BGP table state: Active
Table ID: ###########
BGP main routing table version ###
BGP NSR Initial initsync version 8 (Reached)
Dampening enabled
Status codes: s suppressed, d damped, h history, * valid, > best
i - internal, r RIB-failure, S stale
Origin codes: i - IGP, e - EGP, ? – incomplete
Network Next Hop Metric LocPrf Weight Path
Route Distinguisher: [RD_number] (default for vrf [vrf_name])
* 1.1.2.0/25 192.168.100.1 0 0 6774 ?
s 1.1.1.0/24 192.168.100.1 0 0 6774 ?
* 192.168.100.0/24 192.168.100.1 0 0 6774 ?
* 192.168.101.0/24 192.168.100.1 0 0 6774 ?
Processed 4 prefixes, 4 paths
2.- With Route refresh capability:
2.1 No soft-reconfiguration configured
RP/0/RSP0/CPU0:Mar 28 22:12:59.745 UTC: bgp[1042]: [iowt] VRF [vrf_name]: [RD] send message type 128, length (incl. header) 23
RP/0/RSP0/CPU0:Mar 28 22:12:59.746 UTC: bgp[1042]: [iowt] VRF [vrf_name]: Send message dump for 192.168.100.1:
RP/0/RSP0/CPU0:Mar 28 22:12:59.747 UTC: bgp[1042]: [iowt] VRF [vrf_name]: ffff ffff ffff ffff ffff ffff ffff ffff
RP/0/RSP0/CPU0:Mar 28 22:12:59.748 UTC: bgp[1042]: [iowt] VRF [vrf_name]: 0017 8000 0100 01
#sh bgp vrf [vrf_name] neighbors [neighbour_address] detail
BGP neighbor is [neighbour_address], vrf GRX
Remote AS ###, local AS ###, external link
<snip>
Neighbor capabilities: Adv Rcvd
Route refresh: Yes Yes
4-byte AS: Yes Yes
Address family IPv4 Unicast: Yes Yes
<snip>
#show bgp vrf [vrf_name] neighbors [neighbour_address] received routes
% The 'show bgp neighbor received routes' command is only available when inbound soft reconfiguration is active.
To activate inbound soft reconfiguration, use the 'soft-reconfiguration inbound' command.
If the neighbor supports route-refresh, the 'always' option to the command must also be specified.
2.2 Soft-reconfiguration configured
RP/0/RSP0/CPU0:Mar 28 22:15:59.571 UTC: bgp[1042]: [iowt] VRF [vrf_name]: [RD] send message type 128, length (incl. header) 23
RP/0/RSP0/CPU0:Mar 28 22:15:21.572 UTC: bgp[1042]: [iowt] VRF [vrf_name]: Send message dump for 192.168.100.1:
RP/0/RSP0/CPU0:Mar 28 22:15:21.573 UTC: bgp[1042]: [iowt] VRF [vrf_name]: ffff ffff ffff ffff ffff ffff ffff ffff
RP/0/RSP0/CPU0:Mar 28 22:15:21.574 UTC: bgp[1042]: [iowt] VRF [vrf_name]: 0017 8000 0100 01
#sh bgp vrf [vrf_name] neighbors [neighbour_address] detail
BGP neighbor is [neighbour_address], vrf GRX
Remote AS ###, local AS ###, external link
<snip>
Neighbor capabilities: Adv Rcvd
Route refresh: Yes Yes
4-byte AS: Yes Yes
Address family IPv4 Unicast: Yes Yes
<snip>
#show bgp vrf [vrf_name] neighbors [neighbour_address] received routes
% The 'show bgp neighbor received routes' command is only available when inbound soft reconfiguration is active.
To activate inbound soft reconfiguration, use the 'soft-reconfiguration inbound' command.
If the neighbor supports route-refresh, the 'always' option to the command must also be specified.
2.3 Soft-reconfiguration always configured
#sh bgp vrf [vrf_name] neighbors [neighbour_address] detail
BGP neighbor is [neighbour_address], vrf GRX
Remote AS ###, local AS ###, external link
<snip>
Neighbor capabilities: Adv Rcvd
Route refresh: Yes Yes
4-byte AS: Yes Yes
Address family IPv4 Unicast: Yes Yes
<snip>
#show bgp vrf [vrf_name] neighbors [neighbour_address] received routes
<snip>
BGP VRF [vrf_name], state: Active
BGP Route Distinguisher: [Route Distinguisher number]
VRF ID: [vrf_id]
BGP router identifier [router-id], local AS number [AS-number]
Non-stop routing is enabled
BGP table state: Active
Table ID: ###########
BGP main routing table version ###
BGP NSR Initial initsync version 8 (Reached)
Dampening enabled
<snip>
Status codes: s suppressed, d damped, h history, * valid, > best
i - internal, r RIB-failure, S stale
Origin codes: i - IGP, e - EGP, ? – incomplete
Network Next Hop Metric LocPrf Weight Path
Route Distinguisher: [RD_number] (default for vrf [vrf_name])
* 1.1.2.0/25 192.168.100.1 0 0 6774 ?
s 1.1.1.0/24 192.168.100.1 0 0 6774 ?
* 192.168.100.0/24 192.168.100.1 0 0 6774 ?
* 192.168.101.0/24 192.168.100.1 0 0 6774 ?
Processed 4 prefixes, 4 paths
Route-Refresh capability | IOS | IOS-XR | ||
No Route-Refresh Capable | Command | Behaviour | Command | Behaviour |
No soft-reconfiguration in configured | RR is not sent | No soft-reconfiguration in configured | RR is not sent | |
No backup table | No backup table | |||
soft-reconfiguration in configured | RR is not sent | soft-reconfiguration in configured | RR is not sent | |
Creates backup table | Creates backup table | |||
Soft-reconfiguration in always | RR is not sent | |||
Creates backup table | ||||
Route-Refresh Capable | Command | Behaviour | Command | Behaviour |
No soft-reconfiguration in configured | RR is sent | No soft-reconfiguration in configured | RR is sent | |
No backup table | No backup table | |||
soft-reconfiguration in configured | RR is not sent | soft-reconfiguration in configured | RR is sent | |
Creates backup table | No backup table | |||
Soft-reconfiguration in always | RR is not sent | |||
Creates backup table |
Regards
Nelson
Nelson Gull | Cisco Systems Limited |
Hi Nelson,
Thank you for explaining this feature.
Do you recommend to use soft-reconfiguration on IGW (A9K RP2 with Tomahawk LC)?
We have multiple eBGP sessions and most of them are sending full BGP RT.
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