Configuration Guide for Cisco NCS 1004, IOS XR Release 25.x.x

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Configuration Guide for Cisco NCS 1004, IOS XR Release 25.x.x

iBGP supports over GCC interfaces

Updated: July 31, 2026

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This concept explains the support for Internal BGP (iBGP) sessions over GCC interfaces in the NCS 1004 system, including route exchange, VRF configuration, and port capabilities for traffic isolation.

iBGP support over GCC interfaces is a routing capability that

  • allows external devices to exchange BGP routes through the management interfaces of NCS 1004 systems,

  • enables NCS 1004 devices to advertise local networks and manage them using BGP-learned paths, and

  • establishes iBGP sessions over GCC for exchanging BGP routes.

You can configure VRF on the GCC management interfaces (port 0 and port 1) of the NCS 1004 device to achieve traffic isolation between the two management ports.

NCS 1004 supports GCC0 and GCC2 interfaces for the 1.2T line card, allowing greater flexibility and connectivity options. The device advertises its local networks using BGP and manages them through paths learned from the iBGP sessions established over the GCC interfaces.

Restrictions for iBGP Support Using GCC

  • IP fragmentation is not supported on the GCC interface.

  • The BGP configuration over Open Config (OC) is not supported.

Note

The limitations of Remote Node Management Using GCC are applicable for iBGP Support Using GCC. For more information, see Limitations of Remote Node Management.

Caution: Follow restrictions for iBGP support using GCC

Consider these restrictions when implementing iBGP support using GCC:

  • Do not use IP fragmentation on the GCC interface; this function is not supported.

  • Do not configure BGP over Open Config (OC) on GCC interfaces; this configuration is not supported.

  • Observe all limitations found for Remote Node Management using GCC; these also apply to iBGP support using GCC

Enabling the GCC Interface

To enable the GCC2 interface, use the following commands:

configure
controller odu4 R/S/I/P/L
gcc2
commit
exit

To enable the GCC0 interface, use the following commands:

configure
controller CoherentDSP R/S/I/P
gcc0
commit
exit

Configuring the Management Interface

To configure the management Ethernet interface with VRF, use the following commands:


RP/0/RP0/CPU0:ios#configure
RP/0/RP0/CPU0:ios#interface MgmtEth0/RP0/CPU0/1
RP/0/RP0/CPU0:ios(config-if)#vrf transport-vrf
RP/0/RP0/CPU0:ios(config-if)#ipv4 address ipv4-address
RP/0/RP0/CPU0:ios(config-if)#commit
RP/0/RP0/CPU0:ios(config-if)#exit

The following example displays how to configure the management Ethernet interface with VRF. 


RP/0/RP0/CPU0:ios#configure
RP/0/RP0/CPU0:ios#interface MgmtEth0/RP0/CPU0/1
RP/0/RP0/CPU0:ios(config-if)#vrf transport-vrf
RP/0/RP0/CPU0:ios(config-if)#ipv4 address 192.0.2.1 255.255.255.255
RP/0/RP0/CPU0:ios(config-if)#commit
RP/0/RP0/CPU0:ios(config-if)#exit

Configuring the Loopback Interface

To configure the loopback interface 0 with VRF, use the following commands: 


RP/0/RP0/CPU0:ios#configure
RP/0/RP0/CPU0:ios#interface Loopback0
RP/0/RP0/CPU0:ios(config-if)#vrf transport-vrf
RP/0/RP0/CPU0:ios(config-if)#ipv4 address ipv4-address
RP/0/RP0/CPU0:ios(config-if)#commit
RP/0/RP0/CPU0:ios(config-if)#exit

The following example displays how to configure the loopback interface 0 with VRF. 


RP/0/RP0/CPU0:ios#configure
RP/0/RP0/CPU0:ios#interface Loopback0
RP/0/RP0/CPU0:ios(config-if)#vrf transport-vrf
RP/0/RP0/CPU0:ios(config-if)#ipv4 address 192.0.2.1 255.255.255.255
RP/0/RP0/CPU0:ios(config-if)#commit
RP/0/RP0/CPU0:ios(config-if)#exit

Configuring the GCC interface

To configure the GCC2 interface with VRF and static IP address, use the following commands:

configure

interface gcc2 R/S/I/P/L

vrf transport-vrf

ipv4 address ipv4-address

commit

exit

To configure the GCC0 interface with VRF and static IP address, use the following commands:

configure

interface gcc0 R/S/I/P

vrf transport-vrf

ipv4 address ipv4-address

commit

exit

Examples

The following sample displays how to configure the GCC2 interface with VRF and static IP address.


RP/0/RP0/CPU0:ios#configure
RP/0/RP0/CPU0:ios(config)#interface gcc2 0/1/0/0/1
RP/0/RP0/CPU0:ios(config-if)#vrf transport-vrf
P/0/RP0/CPU0:ios(config-if)#ipv4 address 198.51.100.5 255.255.255.0
RP/0/RP0/CPU0:ios(config-if)#commit
RP/0/RP0/CPU0:ios(config-if)#exit
RP/0/RP0/CPU0:ios(config)#exit

The following sample displays how to configure the GCC2 interface using loopback IP address.


RP/0/RP0/CPU0:ios#configure
RP/0/RP0/CPU0:R2(config)#interface gcc2 0/1/0/0/1
RP/0/RP0/CPU0:R2(config-if)#ipv4 unnumbered loopback 0
RP/0/RP0/CPU0:ios(config-if)#exit
RP/0/RP0/CPU0:ios(config)#exit

The following sample displays how to configure the GCC0 interface with VRF and static IP address.


RP/0/RP0/CPU0:ios#configure
RP/0/RP0/CPU0:ios(config)#interface gcc0 0/1/0/0
RP/0/RP0/CPU0:ios(config-if)#vrf transport-vrf
P/0/RP0/CPU0:ios(config-if)#ipv4 address 198.51.100.2 255.255.255.0
RP/0/RP0/CPU0:ios(config-if)#commit
RP/0/RP0/CPU0:ios(config-if)#exit
RP/0/RP0/CPU0:ios(config)#exit

The following sample displays how to configure the GCC0 interface using the loopback IP address.


RP/0/RP0/CPU0:ios#configure
RP/0/RP0/CPU0:R2(config)#interface gcc0 0/1/0/0
RP/0/RP0/CPU0:R2(config-if)#ipv4 unnumbered loopback 0
RP/0/RP0/CPU0:ios(config-if)#exit
RP/0/RP0/CPU0:ios(config)#exit

Verifying iBGP Support Using GCC

To verify BGP support using GCC configuration, use the following show commands:


RP/0/RP0/CPU0:ios#show bgp vrf transport-vrf neighbors brief
Neighbor        Spk    AS Description                          Up/Down  NBRState
198.51.100.0     0     200                                    00:51:49 Established
198.51.100.1       0    100                                    00:50:32 Established


RP/0/RP0/CPU0:ios#show bgp vrf transport-vrf                                        
BGP VRF transport-vrf, state: Active                                               
BGP Route Distinguisher: 192.0.2.7:0                                                 
VRF ID: 0x60000002                                                                 
BGP router identifier 192.0.2.7, local AS number 100                                 
Non-stop routing is enabled                                                        
BGP table state: Active                                                            
Table ID: 0xe0000002   RD version: 51                                              
BGP main routing table version 51                                                  
BGP NSR Initial initsync version 11 (Reached)                                      
BGP NSR/ISSU Sync-Group versions 0/0                                               
 
Status codes: s suppressed, d damped, h history, * valid, > best
              i - internal, r RIB-failure, S stale, N Nexthop-discard
Origin codes: i - IGP, e - EGP, ? - incomplete                      
   Network            Next Hop            Metric LocPrf Weight Path 
Route Distinguisher: 192.0.2.7:0 (default for vrf transport-vrf)      

*> 209.165.201.30/27        198.51.100.0              0         0 200 i
*> 209.165.201.28/27        0.0.0.0                   0         32768 i    
*> 209.165.201.26/27        0    100      0 i      
*> 209.165.201.24/27       198.51.100.2               0    100      0 300 i



RP/0/RP0/CPU0:ios#show bgp vrf transport-vrf                                        
BGP VRF transport-vrf, state: Active                                               
BGP Route Distinguisher: 203.0.113.10:0                                                 
VRF ID: 0x60000002                                                                 
BGP router identifier 203.0.113.10, local AS number 100                                 
Non-stop routing is enabled                                                        
BGP table state: Active                                                            
Table ID: 0xe0000002   RD version: 51                                              
BGP main routing table version 51                                                  
BGP NSR Initial initsync version 11 (Reached)                                      
BGP NSR/ISSU Sync-Group versions 0/0                                               
 
Status codes: s suppressed, d damped, h history, * valid, > best
              i - internal, r RIB-failure, S stale, N Nexthop-discard
Origin codes: i - IGP, e - EGP, ? - incomplete                      
   Network            Next Hop            Metric LocPrf Weight Path 
Route Distinguisher: 203.0.113.10:0 (default for vrf transport-vrf)      

*> 209.165.201.30/27        198.51.100.0              0             0 200 i
*> 209.165.201.28/27        0.0.0.0                   0             32768 i    
*>i209.165.201.26/27        198.51.100.12               0    100      0 i      
*>i209.165.201.24/27       198.51.100.24               0    100      0 300 i

iBGP configuration parameters for GCC interfaces

This table summarizes the configuration required for enabling iBGP sessions between two NCS 1004 devices.

Use case:

Consider two NCS 1004 devices, R2 and R3, directly connected through GCC0 interfaces. In this use case, R2 (with IP address 198.51.100.21) and R3 (with IP address 198.51.100.22) are configured with the commands to establish an iBGP session using their respective transport-VRFs.

R2 is connected through GCC0 0/0/0/0 interface with IP address of 198.51.100.21 and R3 is connected through GCC0 0/1/0/0 with IP address of 198.51.100.22. The R2 and R3 devices are connected to external devices through management interfaces.

Table 1. iBGP configuration commands for NCS 1004

Configuration on R2

Configuration on R3

Global Configuration on R2


hw-module location 0/0
 mxponder
  trunk-rate 600G
  client-rate 100GE

vrf transport-vrf
 address-family ipv4 unicast

Global Configuration on R3


hw-module location 0/0
 mxponder
  trunk-rate 600G
  client-rate 100GE

vrf transport-vrf
 address-family ipv4 unicast

Interface Configuration on R2


interface Loopback0
 vrf transport-vrf
 ipv4 address 192.0.2.2 255.255.255.255

interface MgmtEth0/RP0/CPU0/1
 vrf transport-vrf
 ipv4 address 198.51.100.25 255.255.255.0

controller ODU40/0/0/0/2
 gcc2

interface GCC20/0/0/0/2
 vrf transport-vrf
 ipv4 address 198.51.100.21 255.255.255.0

Interface Configuration on R3


interface Loopback0
 vrf transport-vrf
 ipv4 address 203.0.113.3 255.255.255.255

interface MgmtEth0/RP0/CPU0/1
 vrf transport-vrf
 ipv4 address 198.51.100.32 255.255.255.0

controller ODU40/1/0/0/2
 gcc2

interface GCC20/1/0/0/2
 vrf transport-vrf
 ipv4 address 198.51.100.22 255.255.255.0

Route-policy Configuration on R2


route-policy PASS-ALL
  pass
end-policy

Router Policy Configuration on R3


route-policy PASS-ALL
  pass
end-policy

Static Route Configuration on R2


router static
 address-family ipv4 unicast
  0.0.0.0/0 198.51.100.28
 !
 vrf transport-vrf
  address-family ipv4 unicast
   198.51.100.0/24 198.51.100.22

Static Route Configuration on R3


router static
 address-family ipv4 unicast
  0.0.0.0/0 198.51.100.28

 vrf transport-vrf
  address-family ipv4 unicast
   198.51.100.0/24 198.51.100.21

BGP Configurationon R2


router bgp 100
 bgp router-id 192.0.2.123
 address-family vpnv4 unicast
 !
 vrf transport-vrf
  rd auto
  address-family ipv4 unicast
   network 203.0.113.1/32
  !
  neighbor 198.51.100.22
   remote-as 100
   address-family ipv4 unicast
    route-policy PASS-ALL in
    route-policy PASS-ALL out
    next-hop-self
   !

BGP Configuration on R3


router bgp 100
 bgp router-id 192.0.2.124
 address-family vpnv4 unicast
 !
 vrf transport-vrf
  rd auto
  address-family ipv4 unicast
   network 203.0.113.3/32
  !
  neighbor 198.51.100.21
   remote-as 100
   address-family ipv4 unicast
    route-policy PASS-ALL in
    route-policy PASS-ALL out
    next-hop-self
   !

BGP Verification on R2


RP/0/RP0/CPU0:ios#show bgp sessions
Mon Jul 20 14:47:30.378 UTC

Neighbor        VRF                   Spk    AS   InQ  OutQ  NBRState     NSRState
198.51.100.22   transport-vrf           0   100     0     0  Established  None

BGP Verification on R3


RP/0/RP0/CPU0:regen#show bgp sessions
Tue Jul 21 02:50:14.134 UTC  

Neighbor        VRF                   Spk    AS   InQ  OutQ  NBRState     NSRState
198.51.100.21   transport-vrf           0   100     0     0  Established  None