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30 An Introduction to IP Routing Protocols

Host routes are managed with Nortel Networks Command Line Interface

(NNCLI) commands and SNMP MIBs and are identiﬁed by the host IP

address and the conﬁgured route type of service (TOS). For each host

directly connected to the router, conﬁgure the cost of the link to the host

during host creation. You cannot modify this cost.

Note: Always set TOS to 0 because TOS-based routing is not

supported.

When a host is added to, or deleted from, a host route, the router updates

the router LSAs and ﬂoods them to neighbors in each area where that

router has an interface.

Following is an example of parameters for a host route advertised in the LSA.

Host route in LSA

•

Type: 3 (stub network)

•

LinkID: IP address of host directly connected to router

•

Link Data: 0xFFFFFFFF

•

Metric: conﬁgured cost of host

OSPF Enhancements

•

Host route - Allows a router to advertise to its neighbors all hosts that

are directly attached to that router’s interfaces. Up to 32 host routes

can be conﬁgured.

•

Virtual links - The OSPF network can be partitioned into multiple

areas. However, a backbone area must exist and be contiguous, and

every non-backbone area must be connected to the backbone area

using either a physical or a logical link. In a network where a physical

connection between the non-backbone area and backbone area is

impossible, use of a virtual link provides the logical connection through

another non-backbone area, called the transit area. Virtual links can be

created manually or automatically. The 5500 Series switch supports

up to 16 virtual links.

When 5500 Series switches are stacked, and a unit leaves the stack and

becomes standalone, the router ID is automatically changed to its default

value if IP blocking is turned off and OSPF is globally enabled. This

prevents duplication of a router ID in the OSPF routing domain. The new

router ID value is temporary, that is, it is not saved to NVRAM. Therefore,

upon reset, the old router ID is restored. Conﬁgurable using NNCLI, ACG,

and Device Manager.

Example conﬁgurations The following is an example for creating a host

route:

Nortel Ethernet Routing Switch 5500 Series

Conﬁguration-IP Routing Protocols

NN47200-503 03.01 Standard

5.1 27 August 2007