VPRN Features
Page 870 7750 SR OS Services Guide
Subscriber Subnet Owned IP Address Connectivity
In order for the network to reliably reach the owned IP addresses on a subscriber subnet, the
owning node must advertise the IP addresses as /32 host routes into the core. This is important
since the subscriber subnet is advertised into the core by multiple routers and the network will
follow the shortest path to the closest available router which may not own the IP address if the /32
is not advertised within the IGP.
Subscriber Subnet SRRP Gateway IP Address Connectivity
The SRRP gateway IP addresses on the subscriber subnets cannot be advertised as /32 host routes
since they may be active (master) on multiple group IP interfaces on multiple SRRP routers.
Without a /32 host route path, the network will forward any packet destined to an SRRP gateway
IP address to the closest router advertising the subscriber subnet. While a case may be made that
only a node that is currently forwarding for the gateway IP address in a master state should
respond to ping or other diagnostic messages, the distribution of the subnet and the case of
multiple masters make any resulting response or non-response inconclusive at best. To provide
some ability to ping the SRRP gateway address from the network side reliably, any node receiving
the ICMP ping request will respond if the gateway IP address is defined on its subscriber subnet.
Receive SRRP Advertisement SAP and Anti-Spoof
The group IP interface SAPs are designed to support subscriber hosts and perform an ingress anti-
spoof function that ensures that any IP packet received on the group IP interface is coming in the
correct SAP with the correct MAC address. If the IP and MAC are not registered as valid
subscriber hosts on the SAP, the packet is silently discarded. Since the SRRP advertisement source
IP addresses are not subscriber hosts, an anti-spoof entry will not exist and SRRP advertisement
messages would normally be silently discarded. To avoid this issue, when a group IP interface
SAP is configured to send and receive SRRP advertisement messages, anti-spoof processing on
the SAP is disabled. This precludes subscriber host management on the SRRP messaging SAP.
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