Enabling Sending Icmp Error Messages - HPE FlexNetwork 10500 Series Configuration Manual

•
SYN wait timer—TCP starts the SYN wait timer after sending a SYN packet. Within the SYN
wait timer if no response is received or the upper limit on TCP connection tries is reached, TCP
fails to establish the connection.
•
FIN wait timer—TCP starts the FIN wait timer when TCP changes the connection state to
FIN_WAIT_2. If no FIN packet is received within the timer interval, TCP terminates the
connection. If a FIN packet is received, TCP changes the connection state to TIME_WAIT. If a
non-FIN packet is received, TCP restarts the timer, and tears down the connection when the
timer expires.
To set TCP timers:
Step
1. Enter system view.
2. Set TCP timers.

Enabling sending ICMP error messages

Perform this task to enable sending ICMP error messages, including redirect, time exceeded, and
destination unreachable messages.
•
ICMP redirect messages
A host that has only one default route sends all packets to the default gateway. The default
gateway sends an ICMP redirect message to inform the host of a correct next hop by following
these rules:
The receiving and sending interfaces are the same.

The selected route is not created or modified by any ICMP redirect messages.

The selected route is not destined for 0.0.0.0.

There is no source route option in the received packet.

ICMP redirect messages simplify host management and enable hosts to gradually optimize
their routing table.
•
ICMP time exceeded messages
A device sends ICMP time exceeded messages by following these rules:
The device sends the source an ICMP TTL exceeded in transit message when the following

conditions are met:
−
−
When the device receives the first fragment of an IP datagram destined for it, it starts a timer.

If the timer expires before all the fragments of the datagram are received, the device sends
an ICMP fragment reassembly time exceeded message to the source.
•
ICMP destination unreachable messages
A device sends ICMP destination unreachable messages by following these rules:
The device sends the source an ICMP network unreachable message when the following

conditions are met:
−
−
Command
system-view
•
Set the TCP SYN wait timer:
tcp timer syn-timeout time-value
•
Set the TCP FIN wait timer:
tcp timer fin-timeout time-value
The received packet is not destined for the device.
The TTL field of the packet is 1.
The packet does not match any route.
No default route exists in the routing table.
143
Remarks
N/A
By default:
•
The TCP SYN wait timer is 75
seconds.
•
The TCP FIN wait timer is 675
seconds.