Redundancy Issues and Multiple Route Reflectors in an AS
With the lack of a full BGP mesh inside the AS, redundancy and reliability become issues. If a route reflector fails, clients will be isolated. Redundancy requires the existence of multiple route reflectors in a cluster where clients can simultaneously peer with multiple routers. If one route reflector fails, the other(s) should still be available. The importance of complementing logical redundancy with physical redundancy cannot be overstated. It does not make sense to bui..
Preventing Suboptimal Routes by Using Route Tags
Another method of preventing suboptimal routing on the redistributing routers is to simply filter theproblematic routes. Using subnet 10.1.2.0/24 as an example again, R3 could use an incomingdistribute-list command to filter the OSPF route to 10.1.2.0/24, allowing R3 to use its RIP route to10.1.2.0/24. R1 would need to perform similar route filtering as well to prevent its suboptimal route. Performing simple route filtering based on IP subnet number works, but the redistribu..
External Routing Information Propagation
Conventional packet forwarding within the core of an IP network requires that external routing information be advertised to all transit routing devices. This is necessary so that packets can be routed based on the destination address that is contained within the network layer header of the packet. To continue the example from previous sections, the core routers in Figure C-2 would have to store all Internet routes so that they could propagate packets between Bay Area customer..
SMTP, defined in RFC 821, is used to provide e-mail services to IP devices over the Internet. Typically, two mail servers "talk" SMTP to exchange e-mail. After the e-mail is exchanged, the users can retrieve their mail from the mail server and read it. This can be done using any mail client, such as Pine, Eudora, Outlook, and so on, which use different protocols, such as Post Office Protocol 3 (POP3), to connect to the server. SMTP uses well-known ports TCP port 25 and UDP po..
Once again, this problem is similar to the RIP, OSPF. First we have to enable the routing protocol on the CE routers, which we do by configuring a new AS number on the CE routers. These devices are part of a different AS than the MPLS cloud, so they must have different AS numbers: Router-CE-A1#configure terminal Enter configuration commands, one per line. End with CNTL/Z. Router-CE-A1(config)#router bgp 65535 Router-CE-A1(config-router)#neighbor 192.168.1.1 remote-a..
