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Chapter 7
BGP's Basic Components
Origin The ORIGIN (Type Code 1) attribute is a well-known manda-
tory attribute used to tell the receiving BGP router the BGP type of the
original source of the NLRI information. The ORIGIN type can be one of
the type codes shown in Table 7.4.
You can override the second option if an eBGP_MULTIHOP configuration is
used. The eBGP_MULTIHOP configuration, which we will discuss in Chapter 8,
can be used when configuring the next hop if two eBGP speakers need to peer
across multiple subnets and the physical connectivity between two eBGP
speakers runs over more than one load-shared link. Do not use this feature if
both iBGP speakers are in the same AS. Another reason to use the eBGP_
MULTIHOP configuration is if you are using a single point-to-multipoint, non-
broadcast multi-access (NBMA) medium, such as Frame Relay.
T A B L E 7 . 3
Path Segment Values
Bit Value
Path Segment
Type
0
Non-defined
1
AS_SET (an unordered list of ASes that the UPDATE
message has traversed)
2
AS_SEQUENCE (an ordered list of ASes that the UPDATE
message has traversed)
3
AS_CONFED_SET (an unordered list of ASes in the local
confederation that the UPDATE message has traversed)
4
AS_CONFED_SEQUENCE (an ordered list of ASes that the
UPDATE message has traversed in the local confederation)
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