MPLS EIGRP SOO

MPLS Eigrp SOO


The EIGRP MPLS VPN PE-CE Site of Origin (SoO) feature introduces SoO support for EIGRP-to-BGP and BGP-to-EIGRP redistribution. The SoO extended community is a BGP extended community attribute that is used to identify routes that have originated from a site so that the re-advertisement of that prefix back to the source site can be prevented.
SoO filtering is configured at the interface level and is used to manage MPLS VPN traffic and to prevent routing loops from occurring in complex and mixed network topologies, such as EIGRP VPN sites that contain both VPN and back door links and Dual Home.
Version support EIGRP cost community, information is already incoded in the particular update and from customer point MPLS network is transparent portion of the EIGRP topology. Normally redistribution will look as external route in EIGRP, but is case of the MPLS this will be a regular route.
Site of Origin (SoO) filtering is configured at the interface level and is used to manage MPLS VPN traffic and to prevent transient routing loops from occurring in complex and mixed network topologies.The SoO extended community is defined on the interface of the backdoor router. It identifies the local site ID, which should match the value that is used on the PE routers that support the same site. When the backdoor router receives an EIGRP update (or reply) from a neighbor across the backdoor link, the router checks the update for an SoO value. If the SoO value in the EIGRP update matches the SoO value on the local backdoor interface, the route is rejected and not added to the EIGRP topology table.

R2 Config:
ip vrf CUST1
 rd 1:5
 route-target export 1:5
 route-target import 1:5
!
interface Loopback0
 ip address 2.2.2.2 255.255.255.0
 ip ospf network point-to-point
!
interface FastEthernet0/0
 ip vrf forwarding CUST1
 ip address 12.1.1.2 255.255.255.0
 duplex auto
 speed auto
!
interface FastEthernet0/1
 ip address 23.1.1.2 255.255.255.0
 duplex auto
 speed auto
 mpls ip
!
router eigrp 100
 auto-summary
 !
 address-family ipv4 vrf CUST1
  redistribute bgp 100 metric 1 1 1 1 1
  network 12.1.1.0 0.0.0.255
  no auto-summary
  autonomous-system 200
 exit-address-family
!
router ospf 10
 log-adjacency-changes
 network 2.2.2.0 0.0.0.255 area 0
 network 23.1.1.0 0.0.0.255 area 0
!
router bgp 100
 no bgp default ipv4-unicast
 bgp log-neighbor-changes
 neighbor 4.4.4.4 remote-as 100
 neighbor 4.4.4.4 update-source Loopback0
 !
 address-family vpnv4
  neighbor 4.4.4.4 activate
  neighbor 4.4.4.4 send-community both
 exit-address-family
 !
 address-family ipv4 vrf CUST1
  redistribute eigrp 200
  no synchronization
 exit-address-family
!
R3 Config:
interface Loopback0
 ip address 3.3.3.3 255.255.255.0
!
interface FastEthernet0/0
 ip address 23.1.1.3 255.255.255.0
 duplex auto
 speed auto
 mpls ip
!
interface FastEthernet0/1
 ip address 34.1.1.3 255.255.255.0
 duplex auto
 speed auto
 mpls ip
!
router ospf 10
 log-adjacency-changes
 network 0.0.0.0 255.255.255.255 area 0
!
R4 Config:
ip vrf CUST1
 rd 1:5
 route-target export 1:5
 route-target import 1:5
!
interface Loopback0
 ip address 4.4.4.4 255.255.255.0
 ip ospf network point-to-point
!
interface FastEthernet0/0
 ip address 34.1.1.4 255.255.255.0
 duplex auto
 speed auto
 mpls ip
!
interface FastEthernet0/1
 ip vrf forwarding CUST1
 ip address 45.1.1.4 255.255.255.0
 duplex auto
 speed auto
!
router eigrp 100
 auto-summary
 !
 address-family ipv4 vrf CUST1
  redistribute bgp 100 metric 1 1 1 1 1
  network 45.1.1.0 0.0.0.255
  auto-summary
  autonomous-system 200
 exit-address-family
!
router ospf 10
 log-adjacency-changes
 network 4.4.4.0 0.0.0.255 area 0
 network 34.1.1.0 0.0.0.255 area 0
!
router bgp 100
 no bgp default ipv4-unicast
 bgp log-neighbor-changes
 neighbor 2.2.2.2 remote-as 100
 neighbor 2.2.2.2 update-source Loopback0
 !
 address-family vpnv4
  neighbor 2.2.2.2 activate
  neighbor 2.2.2.2 send-community both
 exit-address-family
 !
 address-family ipv4 vrf CUST1
  redistribute eigrp 200
  no synchronization
 exit-address-family

R1 Config:
interface Loopback0
 ip address 1.1.1.1 255.255.255.0
!
interface FastEthernet0/0
 ip address 12.1.1.1 255.255.255.0
 duplex auto
 speed auto
!
interface FastEthernet0/1
 no ip address
 shutdown
 duplex auto
 speed auto
!
router eigrp 200
 network 0.0.0.0
 no auto-summary

R5 Config:
interface Loopback0
 ip address 5.5.5.5 255.255.255.0
!
interface FastEthernet0/0
 ip address 45.1.1.5 255.255.255.0
 duplex auto
 speed auto
!
interface FastEthernet0/1
 no ip address
 shutdown
 duplex auto
 speed auto
!
router eigrp 200
 network 0.0.0.0
 no auto-summary

Site of Origin (SoO) EIGRP

SoO is an extended community attribute used to prevent routing loops in multi-honed MPLS customer sites by tagging and filtering prefixes before being redistributed into the domain of origin.

we can see that the route to self loopback is being learned via the two paths one is directly connected and other is via the serial link, creating loop.

R2:
route-map SOO permit 10
 set extcommunity soo 11:55
!
interface FastEthernet0/0
 ip vrf forwarding CUST1
ip vrf sitemap SOO
 ip address 12.1.1.2 255.255.255.0
 duplex auto
 speed auto
R4:
route-map SOO permit 10
 set extcommunity soo 55:11
!
interface FastEthernet0/1
 ip vrf forwarding CUST1
 ip vrf sitemap SOO
 ip address 45.1.1.4 255.255.255.0
 duplex auto
 speed auto
end







To not learn the same route via backdoor link SOO needs to be configure on the CE's, so that the matching SOO routes can be filtered from re-entering.
R1:
route-map SOO permit 10
 set extcommunity soo 11:55
!
interface Serial1/0
 ip vrf sitemap SOO
 ip address 15.1.1.1 255.255.255.0
 serial restart-delay 0
R5:
route-map SOO permit 10
set extcommunity soo 55:11
!
interface Serial1/0
 ip vrf sitemap SOO
 ip address 15.1.1.5 255.255.255.0