Nortel Networks NN47200-503 manual Equal Cost MultiPath Ecmp, UDP broadcast forwarding

38An Introduction to IP Routing Protocols

Equal Cost MultiPath (ECMP)

The Equal Cost MultiPath (ECMP) feature allows routers to determine equal cost paths to the same destination prefix. The multiple paths can be used for load sharing of traffic and allows faster convergence to other active paths in case of network failure. By maximizing load sharing among equal-cost paths, links between routers can be used more efficiently when sending IP traffic. The ECMP feature supports and complements the following protocols types:

•Open Shortest Path First (OSPF)

•Routing Information Protocol (RIP)

•Static Routes

ECMP is only supported on the Nortel Ethernet Routing Switch 5520 and 5530. ECMP will work in a mixed stack but will not run on any Nortel Ethernet Routing Switch 5510 units in the stack.

UDP broadcast forwarding

Some network applications, such as the NetBIOS name service, rely on User Datagram Protocol (UDP) broadcasts to request a service or locate a application. If a host is on a network, subnet segment, or VLAN that includes a server for the service, UDP broadcasts are by default not forwarded to the server located on a different network segment or VLAN. This is resolved by forwarding the broadcasts to the server through physical or virtual interfaces.

UDP broadcast forwarding is a general mechanism for selectively forwarding limited UDP broadcasts received on an IP interface to a configured IP address. The packet is sent as a unicast packet to the server.

The following are the basic steps for UDP broadcast forwarding configuration:

1.Enter the UDP protocols to be forwarded.

2.Create forwarding policies by defining UDP protocol and server pairs.

3.Assemble these policies into lists.

4.Apply these lists to the appropriate interfaces.

When a UDP broadcast is received on a router interface, it must meet the following criteria if it is to be considered for forwarding:

•It must be a MAC-level broadcast.

•It must be an IP-limited broadcast.

•It must be for a configured UDP protocol.

•It must have a TTL value of at least 2.

Nortel Ethernet Routing Switch 5500 Series

Configuration-IP Routing Protocols

NN47200-503 03.01 Standard

5.127 August 2007

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