API Guide

Figure 22. 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 previous illustration. If Router B has an inbound route-map applied on Router C to prepend "65001 65002" to
the as-path, the following events take place on Router B:
1. Receive and validate the update.
2. Prepend local-as 200 to as-path.
3. Prepend "65001 65002" to as-path.
Local-AS is prepended before the route-map to give an impression that update passed through a router in AS 200 before it
reached Router B.
BGP4 Management Information Base (MIB)
The FORCE10-BGP4-V2-MIB enhances support for BGP management information base (MIB) with many new simple network
management protocol (SNMP) objects and notifications (traps) defined in draft-ietf-idr-bgp4-mibv2-05. To see these
enhancements, download the MIB from the Dell website.
NOTE: For the Force10-BGP4-V2-MIB and other MIB documentation, refer to the Dell iSupport web page.
Important Points to Remember
● Because eBGP packets are not controlled by the ACL, packets from BGP neighbors cannot be blocked using the deny ip
command.
● The f10BgpM2AsPathTableEntry table, f10BgpM2AsPathSegmentIndex, and f10BgpM2AsPathElementIndex are used to
retrieve a particular ASN from the AS path. These indices are assigned to the AS segments and individual ASN in each
segment starting from 0. For example, an AS path list of {200 300 400} 500 consists of two segments: {200 300 400} with
segment index 0 and 500 with segment index 1. ASN 200, 300, and 400 are assigned 0, 1, and 2 element indices in that
order.
● Unknown optional transitive attributes within a given path attribute (PA) are assigned indices in order. These indices
correspond to the f10BgpM2PathAttrUnknownIndex field in the f10BgpM2PathAttrUnknownEntry table.
● Negotiation of multiple instances of the same capability is not supported. F10BgpM2PeerCapAnnouncedIndex and
f10BgpM2PeerCapReceivedIndex are ignored in the peer capability lookup.
Border Gateway Protocol (BGP)
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