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AS Number Migration
With this feature you can transparently change the AS number of an entire BGP network and ensure that the routes are propagated
throughout the network while the migration is in progress.
When migrating one AS to another, perhaps combining ASs, an eBGP network may lose its routing to an iBGP if the ASN changes.
Migration can be difficult as all the iBGP and eBGP peers of the migrating network must be updated to maintain network reachability.
Essentially, Local-AS provides a capability to the BGP speaker to operate as if it belongs to "virtual" AS network besides its physical
AS network.
The following illustration shows a scenario where Router A, Router B, and Router C belong to AS 100, 200, and 300, respectively.
Router A acquired Router B; Router B has Router C as its customer. When Router B is migrating to Router A, it must maintain the
connection with Router C without immediately updating Router C’s configuration. Local-AS allows this behavior to happen by
allowing Router B to appear as if it still belongs to Router B’s old network (AS 200) as far as communicating with Router C is
concerned.
Figure 28. Before and After AS Number Migration with Local-AS Enabled
When you complete your migration, and you have reconfigured your network with the new information, disable this feature.
If you use the “no prepend” option, the Local-AS does not prepend to the updates received from the eBGP peer. If you do not select
“no prepend” (the default), the Local-AS is added to the first AS segment in the AS-PATH. If an inbound route-map is used to
prepend the as-path to the update from the peer, the Local-AS is added first. For example, consider the topology described in the
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Border Gateway Protocol IPv4 (BGPv4)
Содержание S4048-ON
Страница 1: ...Dell Configuration Guide for the S4048 ON System 9 9 0 0 ...
Страница 146: ...Figure 14 BFD Three Way Handshake State Changes 146 Bidirectional Forwarding Detection BFD ...
Страница 477: ...Figure 68 Inspecting Configuration of LAG 10 on ALPHA Link Aggregation Control Protocol LACP 477 ...
Страница 480: ...Figure 70 Inspecting a LAG Port on BRAVO Using the show interface Command 480 Link Aggregation Control Protocol LACP ...
Страница 481: ...Figure 71 Inspecting LAG 10 Using the show interfaces port channel Command Link Aggregation Control Protocol LACP 481 ...
Страница 522: ...Figure 87 Configuring Interfaces for MSDP 522 Multicast Source Discovery Protocol MSDP ...
Страница 523: ...Figure 88 Configuring OSPF and BGP for MSDP Multicast Source Discovery Protocol MSDP 523 ...
Страница 524: ...Figure 89 Configuring PIM in Multiple Routing Domains 524 Multicast Source Discovery Protocol MSDP ...
Страница 528: ...Figure 91 MSDP Default Peer Scenario 1 528 Multicast Source Discovery Protocol MSDP ...
Страница 529: ...Figure 92 MSDP Default Peer Scenario 2 Multicast Source Discovery Protocol MSDP 529 ...
Страница 530: ...Figure 93 MSDP Default Peer Scenario 3 530 Multicast Source Discovery Protocol MSDP ...
Страница 633: ...Policy based Routing PBR 633 ...
Страница 777: ...Figure 119 Single and Double Tag TPID Match Service Provider Bridging 777 ...
Страница 778: ...Figure 120 Single and Double Tag First byte TPID Match 778 Service Provider Bridging ...