Virtual Private Routed Network Services
7750 SR OS Services Guide Page 865
SRRP Messaging
SRRP uses the same messaging format as VRRP with slight modifications. The source IP address
is derived from the system IP address assigned to the local router. The destination IP address and
IP protocol are the same as VRRP (224.0.0.18 and 112, respectively).
The message type field is set to 1 (advertisement) and the protocol version is set to 8 to
differentiate SRRP message processing from VRRP message processing.
The vr-id field has been expanded to support an SRRP instance ID of 32 bits.
Due to the large number of subnets backed up by SRRP, only one message every minute carries
the gateway IP addresses associated with the SRRP instance. These gateway addresses are stored
by the local SRRP instance and are compared with the gateway addresses associated with the local
subscriber IP interface.
Unlike VRRP, only two nodes may participate in an SRRP instance due the explicit association
between the SRRP instance group IP interface, the associated redundant IP interface and the
multi-chassis synchronization (MCS) peering. Since only two nodes are participating, the VRRP
skew timer is not utilized when waiting to enter the master state. Also, SRRP always preempts
Backup
(redundant IP inter-
face not available)
• Will respond to
ARP for all owned
subscriber subnet
IP addresses
(hardware address
and source MAC =
group IP interface
native MAC).
• Will not respond to
ARP for subscriber
subnet SRRP
gateway IP
addresses.
• Will not respond to
ARP for any
subscriber hosts on
the subscriber
subnet.
• Will not respond to
ARP for any
remote IP hosts.
• Will route out the
group IP interface
for subscriber hosts
associated with the
subscriber subnet
using the group IP
interface native
MAC address.
• Subscriber hosts
mapped to the
redundant IP
interface are
remapped to the
group IP interface.
• Will not accept
packets destined to
the SRRP gateway
MAC received on
the group IP
interface.
Table 1: SRRP State Effect on Subscriber Hosts Associated with Group IP Interface (Continued)
SRRP State ARP Local Proxy ARP
Enabled
Remote Proxy
ARP Enabled
Subscriber Host
Routing
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