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Routing & Switching · Intermediate

Update-Source

A BGP neighbor option that sets the source interface (usually a loopback) for the TCP session.

Definition

When peering to a loopback, the local router must source its packets from its loopback so the remote peer sees the expected address. Without it, the session stays in Active or Idle. Junos uses local-address.

Example

neighbor 10.255.0.2 update-source Loopback0

Exam tip

Peering loopback-to-loopback requires update-source on both sides plus IGP reachability between loopbacks.

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