A BGP router considers each neighbor to be either an internal BGP (iBGP) peer or an external BGP (eBGP) peer. Each BGP router resides in a single AS, so neighbor relationships are either with other routers in the same AS (iBGP neighbors) or with routers in other autonomous systems (eBGP neighbors). The two types of neighbors differ only slightly in regard to forming neighbor relationships, with more significant differences in how the type of neighbor (iBGP or eBGP) impacts th..
Default, Primary, and Backup, Plus Full and Partial Routing
In multihoming to different providers, accepting full routes from either or both providers isnot really necessary unless the customer plans to be a provider itself and pass along full routesto its customers (act as a transit AS). Figure 7-16 illustrates a relevant environment. Figure 7-16. Multihoming to Two Providers with Full and Partial Routing The customer can accept full routing from one or both providers, depending on whether thecustomer requires effective load b..
Before transmitting frames, a station must first gain access to the medium, which is a radio channel that stations share. The 802.11 standard defines two forms of medium access: ■ Distributed coordination function (DCF) ■ Point coordination function (PCF) DCF is mandatory and based on the carrier sense multiple access with collision avoidance (CSMA/CA) protocol. With DCF, 802.11 stations contend for access and attempt to send frames when there is no other station transm..
Routing Policy and the Routing Arbiter Service
Remember that NSFNET has been using a Policy Routing DataBase (PRDB) since 1989, both to prevent routing loops when EGP was used between the backbone and the regionals, and to ensure that each regional announced correct routing information. (Incorrect information could be announced simply due to configuration errors in the regional networks.) When it was introduced, BGP made loop detection easy by virtue of its path attribute. If an AS appears in the path twice, the route i..
To use Bidirectional PIM, you must configure all of the routers in your network to support this method of building multicast forwarding trees. The RP configuration looks like this: Router-RP1#configure terminal Enter configuration commands, one per line. End with CNTL/Z. Router-RP1(config)#ip multicast-routing Router-RP1(config)#ip pim bidir-enable Router-RP1(config)#ip pim rp-address 192.168.12.1 bidir Router-RP1(config)#ip pim rp-candidate Loopback0 group-list ..
