Segmenting the AS with Multiple Regions Separated by EBGP
If flexible policies are required between regions to direct traffic accordingly, for instance, each region can be represented as a separate autonomous system. EBGP operates between ASs, and IBGP is run within each AS. You can use a separate IGP if there is an additional requirement for a dynamic routing protocol to establish reachability between EBGP peers. Figure 9-15 illustrates this AS segmentation method. Figure 9-15. Multiple Regions Separated by EBGP At first gl..
Using Regular Expressions to Match AS_PATH
A Cisco IOS AS_PATH filter has one or more configured lines, with each line requiring a regex. The logic is then applied as follows: 1. The regex of the first line in the list is applied to the AS_PATH of each route. 2. For matched NLRI, the NLRI is passed or filtered based on that AS_PATH filter’s configured permit or deny action. 3. For unmatched NLRI, Steps 1 and 2 are repeated, using the next line in the AS_PATH filter, analyzing all NLRI yet to be matched by this ..
Differentiated Packet Servicing
Conventional IP packet forwarding uses only the IP destination address contained within the Layer 3 header within a packet to make a forwarding decision. The hop-by-hop destination-only paradigm used today prevents a number of innovative approaches to network design and traffic flow optimization. In Figure C-2, for example, the direct link between the San Francisco core router and the Washington core router forwards the traffic entering the network in any of the Bay Area Poin..
You can use the following commands to restrict SNMP access to portions of the MIB tree. This example shows the legacy configuration method: Router#configure terminal Enter configuration commands, one per line. End with CNTL/Z. Router(config)#access-list 99 permit 172.25.1.0 0.0.0.255 Router(config)#access-list 99 deny any log Router(config)#snmp-server view ORAVIEW mib-2 included Router(config)#snmp-server view ORAVIEW at excluded Router(config)#snmp-server view ORAVIE..
OSPF area design requires the use of a backbone area, area 0, with each area connecting to area 0 through an ABR. However, in some cases two backbone areas exist; in other cases, a nonbackbone area may not have a convenient point of connection to the backbone area, for example: Case 1. An existing internetwork needs to add a new area, with a convenient, low-cost connection point with another nonbackbone area. However, that connection does not give the new area any conn..
