Troubleshooting A Dhcp Relay Configuration; Ip Performance; Configuring Tcp Attributes - 3Com Switch 7700 Configuration Manual

68 C 4: N
HAPTER ETWORK
Troubleshooting a DHCP
Relay Configuration

IP Performance

Configuring TCP
Attributes
P O
ROTOCOL PERATION
8 Show the configuration of DHCP server groups in User view.
<SW7700> display dhcp-server 1
9 Show the DHCP Server Group number corresponding to the VLAN interface in
User view.
<SW7700> display dhcp-server interface vlan-interface 2
<SW7700> display dhcp-server interface vlan-interface 3
Perform the following procedure if a user cannot apply for an IP address
dynamically:
1 Use the display dhcp-server groupNo command to check if the IP address of the
corresponding DHCP server has been configured.
2 Use the display VLAN and display IP commands to check if the VLAN and the
corresponding interface IP address have been configured.
3 Ping the configured DHCP Server to ensure that the link is connected.
4 Ping the IP address of the VLAN interface of the switch to where the DHCP user is
connected from the DHCP server to make sure that the DHCP server can correctly
find the route of the network segment the user is on. If the ping execution fails,
check if the default gateway of the DHCP server has been configured as the
address of the VLAN interface that it locates on.
5 If no problems are found in the last two steps, use the display dhcp-server
groupNo command to view the packet that has been received. If you only see the
Discover packet and there is no response packet, it means the DHCP Server has
not sent the message to the Switch 7700. In this case, check if the DHCP Server
has been configured properly. If the numbers of request and response packets are
normal, enable the debugging dhcp-relay in User view and then use the terminal
debugging command to output the debugging information to the console. In
this way, you can view the detailed information of all DHCP packets on the
console while applying for the IP address, thereby, conveniently locating the
problem.
IP performance configuration includes:

Configuring TCP Attributes

■
Configuring Special IP Packet Transmission to the CPU
■
Configuring L3 Broadcast Forwarding
■
Displaying and Debugging IP Performance
■
Troubleshooting IP Performance
■
The TCP attributes that can be configured include:
■ synwait timer
response packets are not received before synwait timeout, the TCP connection
will be terminated. The timeout of synwait timer ranges 2 to 600 seconds and
it is 75 seconds by default.
■ finwait timer
FIN_WAIT_2, finwait timer will be started. If FIN packets are not received before
: When sending the syn packets, TCP starts the synwait timer. If
: When the TCP connection state turns from FIN_WAIT_1 to