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FTOS Configuration Guide for the C-Series - Force10 Networks

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When you complete your migration, and you have reconfigured your network with <strong>the</strong> new in<strong>for</strong>mation<br />

you must disable this feature.<br />

If <strong>the</strong> “no prepend” option is used, <strong>the</strong> local-as will not be prepended to <strong>the</strong> updates received from <strong>the</strong><br />

eBGP peer. If “no prepend” is not selected (<strong>the</strong> default), <strong>the</strong> local-as is added to <strong>the</strong> first AS segment in <strong>the</strong><br />

AS-PATH. If an inbound route-map is used to prepend <strong>the</strong> as-path to <strong>the</strong> update from <strong>the</strong> peer, <strong>the</strong> local-as<br />

is added first. For example, consider <strong>the</strong> topology described in Figure 343. If Router B has an inbound<br />

route-map applied on Router C to prepend "65001 65002" to <strong>the</strong> as-path, <strong>the</strong> following events will take<br />

place on Router B<br />

1. Receive and validate <strong>the</strong> update<br />

2. Prepend local-as 200 to as-path<br />

3. Prepend "65001 65002" to as-path<br />

Local-as is prepended be<strong>for</strong>e <strong>the</strong> route-map to give an impression that update passed thru a router in AS<br />

200 be<strong>for</strong>e it reached Router B.<br />

BGP4 Management In<strong>for</strong>mation Base (MIB)<br />

The FORCE10-BGP4-V2-MIB enhances <strong>FTOS</strong> BGP Management In<strong>for</strong>mation Base (MIB) support with<br />

many new SNMP objects and notifications (traps) defined in <strong>the</strong> draft-ietf-idr-bgp4-mibv2-05. To see <strong>the</strong>se<br />

enhancements, download <strong>the</strong> MIB from <strong>the</strong> <strong>Force10</strong> website, www.<strong>for</strong>ce10networks.com.<br />

Note: See <strong>the</strong> <strong>Force10</strong> iSupport webpage <strong>for</strong> <strong>the</strong> <strong>Force10</strong>-BGP4-V2-MIB and o<strong>the</strong>r MIB documentation.<br />

Important Points to Remember<br />

• In f10BgpM2AsPathTableEntry table, f10BgpM2AsPathSegmentIndex, and<br />

f10BgpM2AsPathElementIndex are used to retrieve a particular ASN from <strong>the</strong> AS path. These indices<br />

are assigned to <strong>the</strong> AS segments and individual ASN in each segment starting from 0. For example, an<br />

AS path list of {200 300 400} 500 consists of two segments: {200 300 400} with segment index 0 and<br />

500 with segment index 1. ASN 200, 300, and 400 are be assigned 0, 1, and 2 element indices in that<br />

order.<br />

• Unknown optional transitive attributes within a given path attribute (PA) are assigned indices in order.<br />

These indices correspond to f10BgpM2PathAttrUnknownIndex field in <strong>the</strong><br />

f10BgpM2PathAttrUnknownEntry table.<br />

• Negotiation of multiple instances of <strong>the</strong> same capability is not supported.<br />

F10BgpM2PeerCapAnnouncedIndex and f10BgpM2PeerCapReceivedIndex are ignored in <strong>the</strong> peer<br />

capability lookup.<br />

• Inbound BGP soft-reconfiguration must be configured on a peer <strong>for</strong><br />

f10BgpM2PrefixInPrefixesRejected to display <strong>the</strong> number of prefixes filtered due to a policy. If BGP<br />

soft-reconfig is not enabled, <strong>the</strong> denied prefixes are not accounted <strong>for</strong>.<br />

• F10BgpM2AdjRibsOutRoute stores <strong>the</strong> pointer to <strong>the</strong> NLRI in <strong>the</strong> peer's Adj-Rib-Out.<br />

<strong>FTOS</strong> <strong>Configuration</strong> <strong>Guide</strong>, version 7.7.1.0 473

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