SOO

SOO uniquely identifies the site that originates a route. It is a BGP extended community that prevents routing loops or suboptimal routing, specifically when a backdoor is present between VPN sites. SOO provides loop prevention in networks with dual-homed sites (sites that are connected to two or more PE routers). You can use it when an IGP is the PE-CE routing protocol. You can also use it when BGP is used between PE and CE, when the as-path loop prevention cannot be trusted anymore. This happens when BGP uses as-override or allowas-in. If the SOO is configured for a CE router and a vpnv4 route is learned with the same SOO, the route must not be put in the VRF routing table on the PE and advertised to the CE. In Figure 7-30, the vpnv4 prefix ...

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