Enterasys Networks X-PeditionTM manual Ospf

IP Routing Protocols

•Dial-on-demand connections.

Retransmissions are governed by the following conditions, among others:

•The retransmission timer is a periodic timer set to 5 seconds.

•A limit in the number of retransmissions will be set, after which the routes learned through the specified circuit are marked as unreachable. The maximum number of retransmissions is configurable. The default value is 36.

•After the maximum number of retransmissions has been reached, requests will continue to be sent out with a polling interval whose default value is 30 seconds. This value is also configurable. Polling will continue until a response is received.

OSPF

The Open Shortest Path First (OSPF) routing protocol is a link-state protocol as defined by RFC- 2328. It supports a replicated database approach to routing where each router has a copy of the database and contributes information to the database describing the local environment of linked routers. All routers piece together the data to obtain a current map of the network. The shortest path is calculated using an algorithm based on entries in the database.

OSPF outperforms RIP as a link-state protocol: it converges faster than RIP, a distance-vector protocol; its longest path is not limited as is RIP’s (to 15); and it supports subnets - a mask is linked with each advertised route. The XSR’s implementation of OSPF permits route redistribution to RIP and vice versa.

Note: OSPF does not learn neighbors over unnumbered WAN interfaces with Firewall functionality enabled.

OSPF commands are provided on the XSR with the following features:

•Set globally with the router ospf and per port with the network <ip address> area: they

support OSPF on LAN and WAN interfaces with these defaults: no authentication, cost 10 (LAN) or Serial (64), dead interval of 40 seconds, hello interval of 10 seconds, priority 1, and 5- second retransmit interval.

•Intra- and inter-areas, and Type 1 and 2 external routing

•Broadcast, point-to-point and point to multi-point models

•Protocol enabled/disabled with router ospf

•Area IDs identified and defined with network

•Address ranges used by ABRs defined by area range

•OSPF priority with ip ospf priority

•Cost to send a packet over interface with ip ospf cost

•Cost for default route sent into a stub area with area default cost

•Stub and NSSA set with area stub and area nssa

•Opaque Link-state Advertisement (LSA) option

•Redistribute RIP into OSPF and vice versa with redistribute rip and redistribute ospf

•Manual and automatic virtual links enabled with area virtual link

•MD5 authentication enabled per interface with area authentication and ip ospf message-digest-key

5-14 Configuring IP