56 SHOW IP ADVERTISE Patch Release Note
Patch 86251-08 for Software Release 2.5.1
C613-10356-00 REV I
Adopting the VRRP IP Address
Benefits The VRRP master router can adopt the IP address of the virtual router (VR), and
respond to the following packets destined for the VR IP address, even if it does
not own this IP address on any of its interfaces:
■ICMP echo requests (pings)
■Telnet and SSH connection requests
■HTTP and SSL GUI management requests
■SNMP requests, and
■DNS relay requests
VRRP IP Address Adoption allows continuous accessibility of the VR IP
address even as the VR master changes. Using this feature:
■You can easily tell whether the VR is functioning, by pinging the single VR
IP address.
■You can easily monitor the performance of the VR, regardless of which
participating router is acting as master.
■DNS relay can continue functioning via the same IP address at all times.
Risks When VR IP Address Adoption is used, the master router accepts packets
destined for the virtual router, even though it may not own this IP address.
This does not conform to RFC 2338. Because the same IP address refers to
different devices at different times, there is a risk of confusion arising. This risk
can be reduced by a suitable network management policy.
Recommendations Before using VR IP address adoption, consider the following guidelines to
avoid confusion:
■Ensure that the VR has an IP address that is different from the interface IP
addresses of any of the individual routers in the VR.
■Ensure that all routers in the virtual router use VRRP IP Address Adoption
(or that none do).
■Use the VR IP address to monitor the VR master. Be aware that this does
not give information about one particular participating router, but about
the current VR master, whichever participating router is acting as the
master at the time.
■When changing the configuration of the participating routers using Telnet,
GUI or SNMP, configure each device individually by pointing to their
individual IP addresses.
■When changing the configuration of the participating routers, do not use
the VR IP addres s. Only one devic e, the VR master, is res ponding to this I P
address, and you may not know which device it is.
Configuration To configure VR IP Address Adoption, use the new parameter, ADOPTVRIP,
that has been added to the CREATE VRRP and SET VRRP commands:
CREATE VRRP=vr-identifier OVER=physical-interface
IPADDRESS=ipadd [ADOPTVRIP={ON|OFF}] [other-vrrp-
parameters]
SET VRRP=vr-identifier [ADOPTVRIP={ON|OFF}] [other-vrrp-
parameters]