Sending and Receiving LSPs

Routers store new LSPs in the link-state database and mark them for flooding. If the LSP is already present in the database, the router just acknowledges it and ignores it. The router sends the new LSP to its neighbors, which in turn flood to their neighbors and so on. Because Level 1 and Level 2 routers have their own link-state databases, Level 1 LSPs are flooded throughout the area; Level 2 LSPs are sent across all Level 2 adjacencies. The process of propagating LSPs diffe..

EIGRP Neighbor Relationships

Unlike IGRP, EIGRP must establish neighbor relationships before updates are sent out. When an EIGRP process is configured on the router, the router begins to exchange EIGRP hello packets over the multicast address of 224.0.0.10. Neighbor relationships form between routers when they receive each other's hello packet. Over LAN broadcast media such as Ethernet, Token Ring, or FDDI, the hello packets are sent every 5 seconds. Over WAN multipoint interfaces with a bandwidth of T1 ..

Cisco IS-IS Restart Operation

This section illustrates the operation of the Cisco IS-IS restart mechanism, using the network diagram shown in Figure 5-8. Both R1 and R2 are Cisco IS-IS restart/NSF-capable and are interconnected via point-to-point links. •    Assume using normal IS-IS procedures, R1 and R2 have synchronized their databases and are ready for forwarding. Suppose a forwarding path exists from "source" to "destination" passing through R1 and R2, and data traffic is being forw..

Finding an IP Route

The EXEC level command to look at the entire IP routing table is: Router>show ip routeCodes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2       E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP    ..

Advanced Access-List Editing

You can insert a single entry into an existing ACL by specifying a sequence number, as follows: Router2#configure terminal          Enter configuration commands, one per line.  End with CNTL/Z.Router2(config)#ip access-list extended OREILLY        Router2(config-ext-nacl)#12 permit tcp any host 172.25.100.100 eq 20Router2(config-ext-nacl)#endRouter2#   The following commands show how t..