Sending Back Icmp Ttl Exceeded Messages For Mpls Ttl Expired Packets - HP 10500 SERIES Configuration Manual

Configuration procedure
To configure TTL propagation of MPLS:
Step
1. Enter system view.
Enter MPLS view.
2.
3. Enable MPLS TTL propagation.
Sending back ICMP TTL exceeded messages for MPLS TTL
expired packets
After you enable an LSR to send back ICMP TTL exceeded messages for MPLS TTL expired packets, when
the LSR receives an MPLS packet that carries a label with TTL being 1, it generates an ICMP TTL exceeded
message, and send the message to the packet sender in one of the following ways:
• If the LSR has a route to the packet sender, it sends the ICMP TTL exceeded message to the packet
sender directly through the IP route.
If the LSR has no route to the packet sender, it forwards the ICMP TTL exceeded message along the
•
LSP to the egress, which sends the message to the packet sender.
Usually, for an MPLS packet carrying only one level of label, the first method is used. For an MPLS packet
carrying a multi-level label stack, the second method is used. However, because autonomous system
boundary routers (ASBRs), superstratum PEs or service provider-end PEs (SPEs) in Hierarchy of VPN
(HoVPN) applications, and carrier backbone PEs in nested VPNs may receive MPLS VPN packets that
carry only one level of labels but these devices have no IP routes to the packet senders, the first method
is not applicable. In this case, you can configure the undo ttl expiration pop command on these devices
so the devices use the second method.
For more information about HoVPN and nested VPN, see
To configure the device to send back an ICMP TTL exceeded message for a received MPLS TTL expired
packet:
Step
1. Enter system view.
2. Enter MPLS view.
3. Enable the device to send
back an ICMP TTL exceeded
message when it receives an
MPLS TTL expired packet.
Command
system-view
mpls
ttl propagate { public | vpn }
Command
system-view
mpls
ttl expiration enable
72
Remarks
N/A
N/A
Optional.
Enabled only for public network
packets by default.
"Configuring MPLS L3VPN."
Remarks
N/A
N/A
Optional.
Enabled by default.
Support for this command depends
on the device model.