MPLS BGP Soo Example

Issue

We have 3 CEs in VRF RED, R4 and R7 have a backdoor link connected between them and they run RIP to advertise their loopbacks

As well, we have BGP as the PE-CE routing protocol and all the CEs are in the same AS number, let us go through and check

Configuration

R1

R1#sh run int f0/0

interface FastEthernet0/0

 ip address 192.1.15.1 255.255.255.0

 speed 100

 full-duplex

 mpls ip

R1#sh run int f0/1

interface FastEthernet0/1

 ip vrf forwarding RED

 ip address 192.1.14.1 255.255.255.0

 speed 100

 full-duplex

R1#sh run int f1/0

interface FastEthernet1/0

 ip vrf forwarding RED

 ip address 192.1.17.1 255.255.255.0

 speed 100

 full-duplex

R1#sh run int lo0

interface Loopback0

 ip address 1.1.1.1 255.255.255.255

R1#sh run | sec ip vrf

ip vrf RED

 rd 200:10

 route-target export 200:10

 route-target import 200:10

R1#sh run | sec router ospf

router ospf 1

 router-id 1.1.1.1

 log-adjacency-changes

 network 1.1.1.1 0.0.0.0 area 0

 network 192.1.15.1 0.0.0.0 area 0

R1#sh run | sec router bgp

router bgp 10

 no synchronization

 bgp log-neighbor-changes

 neighbor 3.3.3.3 remote-as 10

 neighbor 3.3.3.3 update-source Loopback0

 neighbor 3.3.3.3 next-hop-self

 no auto-summary

 !

 address-family vpnv4

  neighbor 3.3.3.3 activate

  neighbor 3.3.3.3 send-community both

 exit-address-family

 !

 address-family ipv4 vrf RED

  neighbor 192.1.14.4 remote-as 200

  neighbor 192.1.14.4 activate

  neighbor 192.1.17.7 remote-as 200

  neighbor 192.1.17.7 activate

  no synchronization

 exit-address-family

R1#sh run | inc mpls

mpls label protocol ldp

 mpls ip

mpls ldp router-id Loopback0 force

R3

R3#sh run int f0/0

interface FastEthernet0/0

 ip vrf forwarding RED

 ip address 192.1.36.3 255.255.255.0

 speed 100

 full-duplex

R3#sh run int lo0

interface Loopback0

 ip address 3.3.3.3 255.255.255.255

R3#sh run | sec router ospf

router ospf 1

 router-id 3.3.3.3

 log-adjacency-changes

 network 3.3.3.3 0.0.0.0 area 0

 network 192.1.23.3 0.0.0.0 area 0

R3#sh run | inc mpls

mpls label protocol ldp

 mpls ip

mpls ldp router-id Loopback0 force

R3#sh run | sec router bgp

router bgp 10

 no synchronization

 bgp log-neighbor-changes

 neighbor 1.1.1.1 remote-as 10

 neighbor 1.1.1.1 update-source Loopback0

 no auto-summary

 !

 address-family vpnv4

  neighbor 1.1.1.1 activate

  neighbor 1.1.1.1 send-community both

 exit-address-family

 !

 address-family ipv4 vrf RED

  neighbor 192.1.36.6 remote-as 200

  neighbor 192.1.36.6 activate

  no synchronization

 exit-address-family

R4

R4#sh run int lo0

interface Loopback0

 ip address 4.4.4.4 255.255.255.255

R4#sh run int f0/0

interface FastEthernet0/0

 ip address 192.1.14.4 255.255.255.0

 speed 100

 full-duplex

R4#sh run int f0/1

interface FastEthernet0/1

 ip address 192.1.47.4 255.255.255.0

 speed 100

 full-duplex

R4#sh run | sec router rip

router rip

 version 2

 network 4.0.0.0

 network 192.1.47.0

 no auto-summary

R4#sh run | sec router bgp

router bgp 200

 no synchronization

 bgp log-neighbor-changes

 network 4.4.4.4 mask 255.255.255.255

 neighbor 192.1.14.1 remote-as 10

 no auto-summary

R6

R6#sh run int f0/0

interface FastEthernet0/0

 ip address 192.1.36.6 255.255.255.0

 speed 100

 full-duplex

R6#sh run int lo0

interface Loopback0

 ip address 6.6.6.6 255.255.255.255

R6#sh run | sec router bgp

router bgp 200

 no synchronization

 bgp log-neighbor-changes

 network 6.6.6.6 mask 255.255.255.255

 neighbor 192.1.36.3 remote-as 10

 no auto-summary

R7

R7#sh run int f0/0

interface FastEthernet0/0

 ip address 192.1.17.7 255.255.255.0

 speed 100

 full-duplex

R7#sh run int f0/1

interface FastEthernet0/1

 ip address 192.1.47.7 255.255.255.0

 speed 100

 full-duplex

R7#sh run int lo0

interface Loopback0

 ip address 7.7.7.7 255.255.255.255

R7#sh run | sec router rip

router rip

 version 2

 network 7.0.0.0

 network 192.1.47.0

 no auto-summary

R7#sh run | sec router bgp

router bgp 200

 no synchronization

 bgp log-neighbor-changes

 network 7.7.7.7 mask 255.255.255.255

 neighbor 192.1.17.1 remote-as 10

 no auto-summary

Verification

R1#sh mpls ld nei

    Peer LDP Ident: 5.5.5.5:0; Local LDP Ident 1.1.1.1:0

        TCP connection: 5.5.5.5.42565 - 1.1.1.1.646

        State: Oper; Msgs sent/rcvd: 12229/12225; Downstream

        Up time: 1w0d

        LDP discovery sources:

          FastEthernet0/0, Src IP addr: 192.1.15.5

        Addresses bound to peer LDP Ident:

          192.1.15.5      192.1.25.5      5.5.5.5      

 

R1#sh ip bgp vpnv4 all summary

BGP router identifier 1.1.1.1, local AS number 10

BGP table version is 10, main routing table version 10

3 network entries using 411 bytes of memory

3 path entries using 204 bytes of memory

4/2 BGP path/bestpath attribute entries using 496 bytes of memory

1 BGP AS-PATH entries using 24 bytes of memory

1 BGP extended community entries using 24 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 1159 total bytes of memory

BGP activity 7/4 prefixes, 10/7 paths, scan interval 15 secs

Neighbor        V    AS MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down  State/PfxRcd

3.3.3.3         4    10   10632   10628       10    0    0 00:08:36        1

192.1.14.4      4   200   10624   10633       10    0    0 1d09h           1

192.1.17.7      4   200    8752    8762       10    0    0 1d09h           1

R1#sh ip bgp vpnv4 all       

BGP table version is 10, local router ID is 1.1.1.1

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: 200:10 (default for vrf RED)

*> 4.4.4.4/32       192.1.14.4               0             0 200 i

*>i6.6.6.6/32       3.3.3.3                  0    100      0 200 i

*> 7.7.7.7/32       192.1.17.7               0             0 200 i

R3#sh mpls ld nei

    Peer LDP Ident: 2.2.2.2:0; Local LDP Ident 3.3.3.3:0

        TCP connection: 2.2.2.2.646 - 3.3.3.3.22664

        State: Oper; Msgs sent/rcvd: 12226/12216; Downstream

        Up time: 1w0d

        LDP discovery sources:

          Serial0/0, Src IP addr: 192.1.23.2

        Addresses bound to peer LDP Ident:

          192.1.25.2      192.1.23.2      2.2.2.2        

R3#sh ip bgp vpnv4 all summ

BGP router identifier 3.3.3.3, local AS number 10

BGP table version is 6, main routing table version 6

3 network entries using 411 bytes of memory

3 path entries using 204 bytes of memory

4/2 BGP path/bestpath attribute entries using 496 bytes of memory

1 BGP AS-PATH entries using 24 bytes of memory

1 BGP extended community entries using 24 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 1159 total bytes of memory

BGP activity 6/3 prefixes, 11/8 paths, scan interval 15 secs

Neighbor        V    AS MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down  State/PfxRcd

1.1.1.1         4    10   10629   10633        6    0    0 00:09:21        2

192.1.36.6      4   200   10636   10639        6    0    0 00:09:19        1

R3#sh ip bgp vpnv4 all    

BGP table version is 6, local router ID is 3.3.3.3

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: 200:10 (default for vrf RED)

*>i4.4.4.4/32       1.1.1.1                  0    100      0 200 i

*> 6.6.6.6/32       192.1.36.6               0             0 200 i

*>i7.7.7.7/32       1.1.1.1                  0    100      0 200 i

R4#sh ip bgp summary

BGP router identifier 4.4.4.4, local AS number 200

BGP table version is 2, main routing table version 2

1 network entries using 117 bytes of memory

1 path entries using 52 bytes of memory

2/1 BGP path/bestpath attribute entries using 248 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 417 total bytes of memory

BGP activity 1/0 prefixes, 1/0 paths, scan interval 60 secs

Neighbor        V    AS MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down  State/PfxRcd

192.1.14.1      4    10   10634   10625        2    0    0 1d09h           0

R4#sh ip bgp

BGP table version is 2, local router ID is 4.4.4.4

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

*> 4.4.4.4/32       0.0.0.0                  0         32768 i

R6#sh ip bgp summary

BGP router identifier 6.6.6.6, local AS number 200

BGP table version is 10, main routing table version 10

1 network entries using 117 bytes of memory

1 path entries using 52 bytes of memory

2/1 BGP path/bestpath attribute entries using 248 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 417 total bytes of memory

BGP activity 6/5 prefixes, 6/5 paths, scan interval 60 secs

Neighbor        V    AS MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down  State/PfxRcd

192.1.36.3      4    10   10639   10636       10    0    0 00:09:39        0

R6#sh ip bgp        

BGP table version is 10, local router ID is 6.6.6.6

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

*> 6.6.6.6/32       0.0.0.0                  0         32768 i

R7#sh ip bgp summary

BGP router identifier 7.7.7.7, local AS number 200

BGP table version is 2, main routing table version 2

1 network entries using 117 bytes of memory

1 path entries using 52 bytes of memory

2/1 BGP path/bestpath attribute entries using 248 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 417 total bytes of memory

BGP activity 1/0 prefixes, 1/0 paths, scan interval 60 secs

Neighbor        V    AS MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down  State/PfxRcd

192.1.17.1      4    10    8763    8753        2    0    0 1d09h           0

R7#sh ip bgp        

BGP table version is 2, local router ID is 7.7.7.7

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

*> 7.7.7.7/32       0.0.0.0                  0         32768 i

R7#sh ip route rip

     4.0.0.0/32 is subnetted, 1 subnets

R       4.4.4.4 [120/1] via 192.1.47.4, 00:00:14, FastEthernet0/1

R4#sh ip route rip

     7.0.0.0/32 is subnetted, 1 subnets

R       7.7.7.7 [120/1] via 192.1.47.7, 00:00:12, FastEthernet0/1

As we can see that neither of the CEs can receive the loopback of any other CEs (which is advertised in BGP) why?

The reason behind that is that the bgp speaker will not accept a route with its own AS number (which is 200 in our case)

The ways to solve this issue is:

• BGP AS-Override
• BGP AllowAS-in

We will go with AS-Override; the configuration will be applied on the PE towards the CE under the address-family ipv4 configuration mode

R1#conf t

R1(config)#router bgp 10

R1(config-router)# address-family ipv4 vrf RED

R1(config-router-af)#neighbor 192.1.17.7 as-override

*Mar  9 06:20:01.078: %BGP-5-ADJCHANGE: neighbor 192.1.17.7 vpn vrf RED Down AS-override change

R1(config)#router bgp 10

R1(config-router)# address-family ipv4 vrf RED

R1(config-router-af)#neighbor 192.1.14.4 as

R1(config-router-af)#neighbor 192.1.14.4 as-override

R1(config-router-af)#end

*Mar  9 06:16:44.762: %BGP-5-ADJCHANGE: neighbor 192.1.14.4 vpn vrf RED Down AS-override change

R3(config)#router bgp 10

R3(config-router)# address-family ipv4 vrf RED

R3(config-router-af)#neighbor 192.1.36.6 as

R3(config-router-af)#neighbor 192.1.36.6 as-override

*Mar  9 06:19:36.374: %BGP-5-ADJCHANGE: neighbor 192.1.36.6 vpn vrf RED Down AS-override change

R4#sh ip bgp    

BGP table version is 4, local router ID is 4.4.4.4

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

*> 4.4.4.4/32       0.0.0.0                  0         32768 i

*> 6.6.6.6/32       192.1.14.1                             0 10 10 i

*> 7.7.7.7/32       192.1.14.1                             0 10 10 i

R6#sh ip bgp    

BGP table version is 4, local router ID is 6.6.6.6

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

*> 4.4.4.4/32       192.1.36.3                             0 10 10 i

*> 6.6.6.6/32       0.0.0.0                  0         32768 i

*> 7.7.7.7/32       192.1.36.3                             0 10 10 i

R7#sh ip bgp

BGP table version is 4, local router ID is 7.7.7.7

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

*> 4.4.4.4/32       192.1.17.1                             0 10 10 i

*> 6.6.6.6/32       192.1.17.1                             0 10 10 i

*> 7.7.7.7/32       0.0.0.0                  0         32768 i

Now , the SOO community is used in MPLS networks to prevent looping between the PEs , when a PE advertise a route to its neighbor PE that is attached with a soo community that matches the same rd configured under the ip vrf configuration mode , it will not advertise it to its CE

Let us configure it on R1 and check

R1#conf t

R1(config)#route-map SOO permit 10

R1(config-route-map)#set extcommunity soo 200:10

R1(config)#router bgp 10

R1(config-router)#address-family ipv4 vrf RED        

R1(config-router-af)#neighbor 192.1.14.4 route-map SOO in

R1(config-router-af)#neighbor 192.1.17.7 route-map SOO in

R1#clear ip bgp *

R1#sh ip bgp vpnv4 vrf RED 6.6.6.6

BGP routing table entry for 200:10:6.6.6.6/32, version 20

Paths: (1 available, best #1, table RED)

  Advertised to update-groups:

     2          3        

  200

    3.3.3.3 (metric 67) from 3.3.3.3 (3.3.3.3)

      Origin IGP, metric 0, localpref 100, valid, internal, best

      Extended Community: RT:200:10

      mpls labels in/out nolabel/23

R1#

R1#

R1#sh ip bgp vpnv4 vrf RED 4.4.4.4

BGP routing table entry for 200:10:4.4.4.4/32, version 14

Paths: (1 available, best #1, table RED)

  Advertised to update-groups:

     1        

  200

    192.1.14.4 from 192.1.14.4 (4.4.4.4)

      Origin IGP, metric 0, localpref 100, valid, external, best

      Extended Community: SoO:200:10 RT:200:10

      mpls labels in/out 29/nolabel

.net file

For anyone want to lab it up, please find the .net file below

autostart = False

[127.0.0.1:7200]

    workingdir = /tmp

    udp = 10001

    [[3725]]

        image = INE/c3725-adventerprisek9-mz.124-18.bin

        ram = 128

        ghostios = True

    [[ROUTER R4]]

        model = 3725

        console = 2004

        aux = 2100

        f0/0 = R1 f0/1

        f0/1 = R7 f0/1

        x = -283.0

        y = 102.0

    [[ROUTER R5]]

        model = 3725

        console = 2005

        aux = 2101

        f0/0 = R1 f0/0

        f0/1 = R2 f0/0

        x = -38.0

        y = -165.0

    [[ROUTER R6]]

        model = 3725

        console = 2006

        aux = 2102

        f0/0 = R3 f0/0

        x = 58.0

        y = 99.0

    [[ROUTER R7]]

        model = 3725

        console = 2007

        aux = 2103

        f0/0 = R1 f1/0

        f0/1 = R4 f0/1

        x = -150.0

        y = 103.0

    [[ROUTER R1]]

        model = 3725

        console = 2001

        aux = 2104

        f0/0 = R5 f0/0

        f0/1 = R4 f0/0

        slot1 = NM-1FE-TX

        f1/0 = R7 f0/0

        x = -223.0

        y = -16.0

    [[ROUTER R2]]

        model = 3725

        console = 2002

        aux = 2105

        wic0/0 = WIC-2T

        s0/0 = FR1 2

        f0/0 = R5 f0/1

        x = 87.0

        y = -87.0

    [[ROUTER R3]]

        model = 3725

        console = 2003

        aux = 2106

        wic0/0 = WIC-2T

        s0/0 = FR1 3

        f0/0 = R6 f0/0

        f0/1 = R8 f0/0

        x = 175.0

        y = -17.0

    [[ROUTER R8]]

        model = 3725

        console = 2008

        aux = 2107

        f0/0 = R3 f0/1

        x = 199.0

        y = 97.0

    [[FRSW FR1]]

        2:203 = 3:302

        3:302 = 2:203

        2 = R2 s0/0

        3 = R3 s0/0

        x = 193.5

        y = -109.5