Refer to the Exhibit.
In the configuration shown in the exhibit, you want to form an EBGP peering relationship to the loopback address of a router administered by your ISP, but the session will not establish.
What is causing the problem?
A.
EBGP cannot peer to a virtual address.
B.
The EBGP session needs to be explicitly configured with multihop.
C.
The EBGP session needs to be explicitly configured as type external.
D.
The autonomous system information needs to be configured under [protocols bgp].
Explanation:
Syntax
multihop {
ttl-value;
no-nexthop-change;
}
Hierarchy Level
[edit logical-systems logical-system-name protocols bgp],
[edit logical-systems logical-system-name protocols bgp group group-name],
[edit logical-systems logical-system-name protocols bgp group group-name neighboraddress],
[edit logical-systems logical-system-name routing-instances routing-instance-name protocols bgp],
[edit logical-systems logical-system-name routing-instances routing-instance-name protocols bgp group group-name],
[edit logical-systems logical-system-name routing-instances routing-instance-name protocols bgp group group-name neighboraddress],
[edit protocols bgp],
[edit protocols bgp group group-name],
[editprotocolsbgpgroupgroup-name neighboraddress],
[edit routing-instances routing-instance-name protocols bgp],
[edit routing-instances routing-instance-name protocols bgp group group-name],
[editrouting-instances routing-instance-name protocols bgp group group-name neighboraddress]Description
Configure an EBGP multihop session.
External confederation peering is a special case that allows unconnected third-party next hops. You do not need to configure multihop sessions explicitly in this particular case; multihop behavior is implied.
If you have confederation external BGP peer-to-loopback addresses, you still need the multihop configuration.Default
If you omit this statement, all EBGP peers are assumed to be directly connected (that is, you are establishing a nonmultihop, or “regular,” BGP session), and the default time-to-live (TTL) value is 1.Options
ttl-valueConfigure the maximum TTL value for the TTL in the IP header of BGP packets.
Range: 1 through 255
Default: 64 (for multihop EBGP sessions, confederations, and internal BGP sessions)
no-nexthop-changeSpecify not to change the BGP next-hop value; for route advertisements, specify the no-nexthop-self option.Configuring an EBGP Multihop Session
If an EBGP peer is more than one hop away from the local router, you must specify the next hop to the peer so that the two systems can establish a BGP session. This type of session is called a multihop BGP session. To configure a multihop session, include the multihop statement:
multihop {
<ttl-value>;
no-nexthop-change;
}
For a list of hierarchy levels at which you can include this statement, see the statement summary section for this statement.To configure the maximum time-to-live (TTL) value for the TTL in the IP header of BGP packets, specify ttl-value. If you do not specify a TTL value, the systems default maximum TTL value is used. To specify not to change the BGP next-hop value for route advertisements, specify the no-nexthop-change option.