BGP SoO is a BGP prolonged neighborhood attribute and stands for BGP Web site of Origin. Web site of Origin uniquely identifies the positioning that has originated the route.
Web site of Origin can be helpful to stop routing loops and suboptimal routing, particularly used to stop routing loops on dual-homed websites.
Web site of Origin can be utilized even when IGP is used between PE-CE routers and can be used when BGP is used between PE-CE routers.
SoO worth must be outlined in one of many beneath Naming Conventions –
- A 16-bit autonomous system quantity, a colon, and a 32-bit quantity, for instance, 45000:3
- A 32-bit IP deal with, a colon, and a 16-bit quantity, for instance, 192.168.10.2:51
BGP SoO Rule of Operation
SOO is utilized on updates coming to PE1 from CE router and when these routes are marketed as VPNV4 path to PE router PE2, the PE2 router doesn’t promote the routes again to the CE router therefore avoiding the routing loop.
Web site of Origin Works & Configuration
Beneath is a situation which can assist perceive extra on how Web site of Origin works and configured:
Within the topology beneath the CE, a router is dual-homed to 2 service supplier PEs (PE1 & PE2). When the routing replace of 9.9.0.1 is acquired on PE1 it imposes Web site of Origin on the incoming replace.
When this routing replace is handed onto PE2 it checks the Web site of Origin tag for this prefix already configured on itself. If the Web site of Origin tag matches the route just isn’t propagated again to the CE.
SCENARIO 1:
Routing replace of 9.9.0.1 is propagated to PE1 and an inbound route-map is utilized to set Web site of Origin worth 200:1 to the incoming replace.
PE2 isn’t having any Web site of Origin worth configured for 9.9.0.1 and is seen to be promoting the route again to CE.
Notice: As we now have configured AS override the CE could settle for the route from PE2 if it has the prefix 9.9.0.1 from a supply which is much less most popular than an replace from PE2.
Configuration:
PE1:
neighbor 9.9.13.1 activate
neighbor 9.9.13.1 send-community
neighbor 9.9.13.1 as-override
no neighbor 9.9.13.1 route-map Inbound-SoO in
exit-address-family
route-map Inbound-SoO allow 10
set local-preference 200
set extcommunity soo 200:1
PE2:
#No SoO utilized#
neighbor 9.9.13.1 activate
neighbor 9.9.13.1 send-community
neighbor 9.9.13.1 as-override
exit-address-family
confirm on PE2 whether it is promoting the 9.9.0.1 prefix again to CE with out an SoO worth configured which may presumably create routing loops.
Paths: (2 obtainable, greatest #1, desk ABC)
Marketed to update-groups:
1
Refresh Epoch 2
100
9.9.13.1 from 9.9.13.1 (9.9.13.1)
Origin IGP, metric 0, localpref 100, legitimate, exterior, greatest
Prolonged Group: RT:23:23
mpls labels in/out 16/nolabel
rx pathid: 0, tx pathid: 0x0
Refresh Epoch 2
100
9.9.0.2 (metric 3) from 9.9.0.4 (9.9.0.4)
Origin IGP, metric 0, localpref 100, legitimate, inside
Prolonged Group: SoO:200:1 RT:23:23
Originator: 9.9.0.2, Cluster listing: 9.9.0.4
mpls labels in/out 16/16
rx pathid: 0, tx pathid: 0
SCENARIO 2:
We apply the Web site of Origin on the router PE2 for 9.9.0.1 prefix and may see now PE2 now doesn’t promote the 9.9.0.1 replace again to the CE router.
neighbor 9.9.13.1 activate
neighbor 9.9.13.1 send-community
neighbor 9.9.13.1 as-override
neighbor 9.9.13.1 route-map Inbound-SoO in
exit-address-family
Output :
PE2#sh ip bgp vpnv4 vrf ABC neighbors 9.9.13.1 advertised-routesWhole variety of prefixes 0
If Web site of Origin is utilized to every other routing protocol than BGP, the route-map configured known as with a ip vrf site-map command.
Instance:
Ip vrf site-map Inbound-SoO
You can too set SoO for related and static routes when they’re redistributed.
Instance :
Redistribute static route-map Inbound-SoO
