Brocade Multi-Service IronWare Administration Guide (Supporting R05.6.00) - Manual (Page 229)

Multi-Service IronWare Administration Guide 211
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LSP ping and traceroute
6
• Router Alert option is set.
By default, the reply mode is set to 2 (reply by way of an IPv4 UDP packet), and you can set it to
1 (no reply) or 3 (reply by way of an IPv4 UDP packet with Router Alert option).
The sender handle is set to an internally-generated, 32-bit number that is assigned to each
ping or traceroute session when the ping or traceroute operation begins. This sender handle is
sent back in the echo reply, which is used to locate the appropriate ping or traceroute session.
The sequence number is a running number associated with each ping or traceroute session. It
is starts with a value of 1.
The TTL for the outermost label is set to 255 for a ping. For traceroute, it is 1, 2, 3, and so on.
You can configure a timeout when starting the ping or traceroute command. The default value
is 5 seconds.
MPLS echo reply
The MPLS echo reply is sent by the transit (for traceroute) or egress (for ping and traceroute) LSR
as a regular IPv4 UDP packet or an IPv4 UDP packet with Router Alert option depending on the
reply-mode field of the echo request. If reply with Router Alert option is chosen, the user should
make sure that all intermediate routers are capable of handling MPLS echo reply. If a reply is sent
with Router Alert option and the reply is sent over a tunnel interface, the MPLS Router Alert label
(label value 1) will be the topmost label for the packet. A reply with a Router Alert option should be
used if and only if the normal IP return path is deemed unreliable.
The echo reply has the following characteristics.
IP/UDP header information:
• Source address = LSR ID
• Destination address = source IP address from the echo request
• UDP source port = 3503
• UDP destination port = UDP source port from the echo request
• IP TTL = 255
• Router Alert option set if and only if reply-mode field of the echo request set to 3.
The sender handle is copied from echo request message
The sequence number is copied from echo request message