2009 August

Aug 21 2009

Option C – Revisited

Its been a while since I looked at this so here is a refresher.

Consider the topology below.

LDP is configured between RR3 and R1 and also between R2 and RR4.

EBGP with label advertisement is configured between R1 and R2.

The interesting this to notice here is that the label advertised between the EBGP peers is actually taken from LDP. ie R1 advertises the LDP label of 18 for 3.3.3.3 as you can see below. You can see it actually states that in the brackets ie (from LDP).

R1#sh ip bgp labels Network Next Hop In label/Out label 1.1.1.1/32 0.0.0.0 imp-null(from LDP)/nolabel 2.2.2.2/32 11.0.0.1 17/imp-null 3.3.3.3/32 10.0.0.2 18(from LDP)/nolabel 4.4.4.4/32 11.0.0.1 20/102 R1#

If you check the LFIB you will see the same label assigned by LDP.

R1#show mpls forwarding-table Local Outgoing Prefix Bytes Label Outgoing Next Hop Label Label or VC or Tunnel Id Switched interface 17 Pop Label 2.2.2.2/32 0 Fa1/0 11.0.0.1 18 Pop Label 3.3.3.3/32 6352 Fa1/1 10.0.0.2 19 Pop Label 11.0.0.1/32 1703 Fa1/0 11.0.0.1 20 102 4.4.4.4/32 1715 Fa1/0 11.0.0.1

R2 receives the prefix 3.3.3.3/32 via eBGP from its neighbor R1 with the label of 18 as you can see below.

R2#sh ip bgp labels Network Next Hop In label/Out label 1.1.1.1/32 11.0.0.2 103/imp-null 2.2.2.2/32 0.0.0.0 imp-null(from LDP)/nolabel 3.3.3.3/32 11.0.0.2 104/18 4.4.4.4/32 10.0.0.6 102(from LDP)/nolabel R2#

Once R2 has this prefix we need to redistribute these prefixes into the IGP, in our case OSPF.

Once again you will notice that the label is LFIB is that of the one in BGP.

Once you have redistributed BGP into OSPF on both R1 and R2, you can then configure a MP-eBGP multihop session between the two route-reflectors ie RR3 and RR4. This should be configured with next-hop-unchanged to ensure the VPN label does not change at any point in the network.

Once the VPNv4 session comes up you will see the route 192.168.3.0/24 drop into VPNA(VRF ZARAR) on RR4.

check and make sure you have full connectivity.

RR4#show ip cef vrf ZARAR 192.168.3.0 192.168.3.0/24 nexthop 10.0.0.5 FastEthernet1/0 label 104 18 RR4#ping vrf ZARAR 192.168.3.1

Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 192.168.3.1, timeout is 2 seconds: .!!!! Success rate is 80 percent (4/5), round-trip min/avg/max = 104/251/360 ms RR4#

Now lets make it a little more complicated ie lets configure VPNA ie VRF ZARAR on R1. R1 will peer vpnv4 with the route-reflector RR3.

Now lets examinte the control plane and the forwading plane.

Control Plane

R1 Generates an incoming VPN label of 16 for prefix 192.168.1.0/24.

R1#sh ip bgp vpnv4 all labels Network Next Hop In label/Out label Route Distinguisher: 1:1 (ZARAR) 192.168.1.0 0.0.0.0 16/nolabel 192.168.3.0 3.3.3.3 nolabel/18 192.168.4.0 4.4.4.4 nolabel/301

R1 advertises the network 192.168.1.0 and its label and nexthop to RR3.

RR3#sh ip bgp vpnv4 all labels Network Next Hop In label/Out label Route Distinguisher: 1:1 (ZARAR) 192.168.1.0 1.1.1.1 nolabel/16 192.168.3.0 0.0.0.0 18/nolabel 192.168.4.0 4.4.4.4 nolabel/301

RR3 then advertises the prefix along with the VPN label and next-hop to RR4.

RR4#sh ip bgp vpnv4 all labels Network Next Hop In label/Out label Route Distinguisher: 1:1 (ZARAR) 192.168.1.0 1.1.1.1 nolabel/16 192.168.3.0 3.3.3.3 nolabel/18 192.168.4.0 0.0.0.0 301/nolabel

As you can see on RR4, prefix 1921.68.1.0 has the original VPN label and next-hop values.

The CEF table within VRF ZARAR on RR4 shows the VPN label next to the transport label.

RR4#sh ip cef VRF ZARAR 192.168.1.0 192.168.1.0/24 nexthop 10.0.0.5 FastEthernet1/0 label 103 16 RR4#

Now lets examine the transport label, in this case the label 103 as seen above.

R1 advertises the network 1.1.1.1 which is the next hop for the prefix 192.168.1.0/24 into BGP and advertised the IPv4 route to R2 with an implicit-null label, which is taken as mentioned below from LDP.

R2 receives the prefix 1.1.1.1/32 prefix along with the implicit null label. R2 then redistributes this prefix and label into LDP.

R2#show mpls forwarding-table Local Outgoing Prefix Bytes Label Outgoing Next Hop Label Label or VC or Tunnel Id Switched interface 100 Pop Label 11.0.0.2/32 13488 Fa1/0 11.0.0.2 102 Pop Label 4.4.4.4/32 708 Fa1/1 10.0.0.6 103 Pop Label 1.1.1.1/32 0 Fa1/0 11.0.0.2 104 18 3.3.3.3/32 6207 Fa1/0 11.0.0.2 R2#

R2 then advertise the prefix and label 103 to RR4 to complete the label switched path.

RR4 now has the transport label required for the VPN prefix 192.168.1.0/24.

RR4#sh ip cef VRF ZARAR 192.168.1.0 192.168.1.0/24 nexthop 10.0.0.5 FastEthernet1/0 label 103 16 RR4#

now lets try and ping 192.168.1.1 from RR4.

RR4#ping vrf ZARAR 192.168.1.1

Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 192.168.1.1, timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 132/162/208 ms RR4#

The configurtion for option C can be found below.

RR3

! hostname RR3 ! ip vrf ZARAR rd 1:1 route-target export 1:1 route-target import 1:1 ! mpls ldp router-id Loopback0 mpls label protocol ldp ! interface Loopback0 ip address 3.3.3.3 255.255.255.255 no clns route-cache ! interface Loopback10 ip vrf forwarding ZARAR ip address 192.168.3.1 255.255.255.0 no clns route-cache ! interface FastEthernet1/0 ip address 10.0.0.2 255.255.255.252 duplex auto speed auto mpls ip no clns route-cache ! router ospf 1 router-id 3.3.3.3 log-adjacency-changes network 0.0.0.0 255.255.255.255 area 0 ! router bgp 1 no bgp default ipv4-unicast bgp log-neighbor-changes neighbor 1.1.1.1 remote-as 1 neighbor 1.1.1.1 update-source Loopback0 neighbor 4.4.4.4 remote-as 2 neighbor 4.4.4.4 ebgp-multihop 10 neighbor 4.4.4.4 update-source Loopback0 ! address-family ipv4 no auto-summary no synchronization network 3.3.3.3 mask 255.255.255.255 exit-address-family ! address-family vpnv4 neighbor 1.1.1.1 activate neighbor 1.1.1.1 send-community extended neighbor 4.4.4.4 activate neighbor 4.4.4.4 next-hop-unchanged neighbor 4.4.4.4 send-community extended exit-address-family ! address-family ipv4 vrf ZARAR redistribute connected no auto-summary no synchronization exit-address-family ! !

! hostname R1 ! ip vrf ZARAR rd 1:1 route-target export 1:1 route-target import 1:1 ! mpls ldp router-id Loopback0 force mpls label protocol ldp ! interface Loopback0 ip address 1.1.1.1 255.255.255.255 ! interface Loopback10 ip vrf forwarding ZARAR ip address 192.168.1.1 255.255.255.0 ! interface FastEthernet1/0 ip address 11.0.0.2 255.255.255.252 mpls bgp forwarding ! interface FastEthernet1/1 ip address 10.0.0.1 255.255.255.252 mpls ip ! router ospf 1 router-id 1.1.1.1 log-adjacency-changes redistribute bgp 1 subnets route-map LOOPBACK0 network 1.1.1.1 0.0.0.0 area 0 network 10.0.0.0 0.255.255.255 area 0 ! router bgp 1 no bgp default ipv4-unicast bgp log-neighbor-changes neighbor 3.3.3.3 remote-as 1 neighbor 3.3.3.3 update-source Loopback0 neighbor 11.0.0.1 remote-as 2 ! address-family ipv4 neighbor 11.0.0.1 activate neighbor 11.0.0.1 send-label no auto-summary no synchronization network 1.1.1.1 mask 255.255.255.255 network 3.3.3.3 mask 255.255.255.255 exit-address-family ! address-family vpnv4 neighbor 3.3.3.3 activate neighbor 3.3.3.3 send-community extended exit-address-family ! address-family ipv4 vrf ZARAR redistribute connected exit-address-family ! ip prefix-list LOOPBACK0 seq 5 permit 4.4.4.4/32 ! route-map LOOPBACK0 permit 10 match ip address prefix-list LOOPBACK0 !

! hostname R2 ! mpls ldp router-id Loopback0 force mpls label range 100 150 mpls label protocol ldp ! interface Loopback0 ip address 2.2.2.2 255.255.255.255 no clns route-cache ! interface FastEthernet1/0 ip address 11.0.0.1 255.255.255.252 duplex auto speed auto mpls bgp forwarding no clns route-cache ! interface FastEthernet1/1 ip address 10.0.0.5 255.255.255.252 duplex auto speed auto mpls ip no clns route-cache ! router ospf 1 log-adjacency-changes redistribute bgp 2 subnets route-map LOOPBACK0 network 2.2.2.2 0.0.0.0 area 0 network 10.0.0.0 0.0.0.255 area 0 ! router bgp 2 bgp router-id 2.2.2.2 bgp log-neighbor-changes neighbor 11.0.0.2 remote-as 1 ! address-family ipv4 neighbor 11.0.0.2 activate neighbor 11.0.0.2 send-label no auto-summary no synchronization network 2.2.2.2 mask 255.255.255.255 network 4.4.4.4 mask 255.255.255.255 exit-address-family ! ip prefix-list LOOPBACK0 seq 5 permit 3.3.3.3/32 ip prefix-list LOOPBACK0 seq 10 permit 1.1.1.1/32 ! ip access-list standard ZARAR permit 11.0.0.2 ! ! route-map LOOPBACK0 permit 10 match ip address prefix-list LOOPBACK0 ! route-map CONNECTED permit 10 match ip address ZARAR !

RR4
! hostname RR4 ! ip vrf ZARAR rd 1:1 route-target export 1:1 route-target import 1:1 ! mpls ldp router-id Loopback0 mpls label range 300 400 mpls label protocol ldp ! interface Loopback0 ip address 4.4.4.4 255.255.255.255 no clns route-cache ! interface Loopback10 ip vrf forwarding ZARAR ip address 192.168.4.1 255.255.255.0 no clns route-cache ! interface FastEthernet1/0 ip address 10.0.0.6 255.255.255.252 duplex auto speed auto mpls ip no clns route-cache ! router ospf 1 log-adjacency-changes network 0.0.0.0 255.255.255.255 area 0 ! router bgp 2 bgp router-id 4.4.4.4 no bgp default ipv4-unicast bgp log-neighbor-changes neighbor 2.2.2.2 remote-as 2 neighbor 2.2.2.2 update-source Loopback0 neighbor 3.3.3.3 remote-as 1 neighbor 3.3.3.3 ebgp-multihop 10 neighbor 3.3.3.3 update-source Loopback0 ! address-family ipv4 no auto-summary no synchronization network 4.4.4.4 mask 255.255.255.255 exit-address-family ! address-family vpnv4 neighbor 3.3.3.3 activate neighbor 3.3.3.3 next-hop-unchanged neighbor 3.3.3.3 send-community extended exit-address-family ! address-family ipv4 vrf ZARAR redistribute connected no auto-summary no synchronization exit-address-family !

By Zarar • CCIE SP, Inter-AS • 0 • Tags: CCIE, CCIE SP, Inter-AS

Inter-AS Option B – Revisited

Option C – Revisited

QPPB

Frame-Relay to VLAN Interworking – AToM

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