Specifications
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The virtual IP address shared by a group of VRRP routers on a given network segment functions as the next-
hop IP address used by neighboring hosts. The VRRP Master router simply forwards packets that have been
received from hosts using the VRRP Master as the next-hop gateway. The existence of a VRRP master and of
one or more VRRP Backups is transparent to the neighboring hosts. The advantage gained from using VRRP
is that it is a default path with higher availability, but it does not require configuration of dynamic routing or
router discovery protocols on every end host. VRRP on ProCurve switches is interoperable with other routers that
support RFC 3768. VRRP operational aspects include the following:
•Preemptive mode, which can be disabled to prevent VRRP router flapping
•Default Advertisement interval of one second
•Default Detection time of 3.6 seconds
Appendix F: OSPF Equal Cost Multipath
In Open Shortest Path First (OSPF), if different subnet destinations in a network are reachable through multiple
equal-cost, next-hop routes, the router chooses the same next-hop route at a given point in time to send traffic
to destinations reachable through that next-hop router. With OSPF Equal Cost Multipath (OSPF-ECMP), routers
support optional load-sharing across redundant links where the network offers two or more equal-cost next-hop
routes for traffic to different subnets. All traffic for different hosts in the same subnet goes through the same next-
hop router. Multiple paths are balanced based on the number of destination subnets. ProCurve’s OSPF-ECMP
feature is interoperable with OSPF-ECMP implementations from various vendors, including Cisco, 3Com, and
Extreme Networks. The ProCurve implementation supports up to four ECMP links, and traffic is load-balanced
on a round-robin basis per source/destination IP address pair. Thus, traffic sharing the same source/destination
IP address will always choose the same path.
Figure F-1: OSPF ECMP example topology
Figure F-1 shows that there are three equal-cost, next-hop paths from Router A to the destination subnets with
load-sharing across redundant links. At any point in time, Router A’s routing table could have information
indicating the following:
Destination subnet Next hop
10.1.0.0/16 Router C
10.2.0.0/16 Router D
10.3.0.0/16 Router B
10.32.0.0/16 Router B
10.42.0.0/16 Router D
10.1.0.0/16
Router C
Equal Cost Next-hop Paths
Router D
Router B
Router A
Router 1 Router 2
Router 3
Router 4
10.2.0.0/16
10.3.0.0/16
10.32.0.0/16
10.42.0.0/16