- Enterasys Security Router User's Guide

IP Routing Protocols
5-14 Configuring IP
• 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.
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
Note: OSPF does not learn neighbors over unnumbered WAN interfaces with Firewall
functionality enabled.