VRRP Components
378 Router Configuration Guide
→ IP header TTL field – Must be equal to 255, the packet must not have traversed
any IP routed hops
→ IP header protocol field – must be 112 (decimal)
• VRRP message checks
→ Version field – Must be set to the value 2
→ Type field – Must be set to the value of 1 (advertisement)
→ Virtual router ID field – Must match one of the configured VRID on the ingress
IP interface (All other fields are dependent on matching the virtual router ID field
to one of the interfaces configured VRID parameters)
→ Priority field – Must be equal to or greater than the VRID in-use priority or be
equal to 0 (Equal to the VRID in-use priority and 0 requires further processing
regarding master/backup and senders IP address to determine validity of the
message)
→ Authentication type field – Must be equal to 0
→ Advertisement interval field – Must be equal to the VRID configured
advertisement interval
→ Checksum field – Must be valid
→ Authentication data fields – Must be ignored.
VRRP messages not meeting the criteria are silently dropped.
Authentication Type 1 – Simple Text Password
The use of type 1 indicates that VRRP advertisement messages are authenticated with a clear
(simple) text password. All virtual routers participating in the virtual router instance must be
configured with the same 8 octet password. Transmitting virtual routers place a value of 1 in
the VRRP advertisement message authentication type field and put the configured simple text
password into the message authentication data field. Receiving virtual routers compare the
message authentication data field with the local configured simple text password based on the
message authentication type field value of 1.
The same checks are performed for type 0 with the following exceptions (the VRRP
specification may require additional checks):
• VRRP message checks
→ Authentication type field – Must be equal to 1
→ Authentication data fields – Must be equal to the VRID configured simple text
password
Any VRRP message not meeting the type 0 verification checks with the exceptions above are
silently discarded.
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