Subscriber Subnet Owned Ip Address Connectivity; Subscriber Subnet Srrp Gateway Ip Address Connectivity; Receive Srrp Advertisement Sap And Anti-Spoof - Alcatel-Lucent 7750 SR OS Service Manual

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Subscriber Subnet Owned IP Address Connectivity

In order for the network to reliably reach the owned IP addresses on a subscriber subnet, it is not

necessary for the owning node to advertise the IP addresses as /32 host routes into the core.

Network reachability to the subscriber subnet is advertised into the IGP core by both of the dual

homing nodes. The shortest path to the subscriber may not always traverse the active path for a

subscriber. In this case, the path traverses the non-active/primary node for the subscriber and the

traffic will be redirected through the redundant interface to the other node through the redundant

interface to the active path. This ensures that all downstream traffic to a given subscriber will

always flow through one node.

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

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.

7750 SR OS Services Guide

if the gateway IP address is defined on its subscriber subnet.

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