Appendix F: Ospf Equal Cost Multipath; Figure E-1: Vrrp Example Topology; Figure F-1: Ospf Ecmp Example Technology - HP ProCurve 6600 Switch Series Technical Overview

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VRRP is an election protocol that dynamically assigns responsibility for a virtual router on a
LAN .
It provides high availability for a default gateway without the need to reconfigure end hosts
Router A

Figure E-1: VRRP example topology

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 HP 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 . HP networking's
OSPF-ECMP feature is interoperable with OSPF-ECMP implementations from various vendors, including Cisco
and Extreme Networks . The HP networking 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 .
Router 1

Figure F-1: OSPF ECMP example technology

Intranet
and/or
Internet
Multiple router interfaces comprise a
virtual router configured with a
common virtual IP address: 10 . 1 . 1 0 . 1
Host: 10 . 1 . 1 0 . 1 0/24
Default Gateway: 10 . 1 . 1 0 . 1
Equal cost next-hop paths
Router B
Router C
Router D
Router A
Router 2
Router B
10 . 1 .0 .0/16
10 .2 .0 .0/16
Router 3
10 .3 .0 .0/16
10 .32 .0 .0/16
Router 4
10 .42 .0 .0/16