Dhcp Troubleshooting; Commands For Monitor And Debug - Edge-Core ES4624-SFP Manual

Note: DHCP server address and TFTP server address must be configured separately
since their receiving UDP protocols are different. It is recommended to use the
combination of command "ip forward-protocol udp <port>" and "ip helper-address
<ipaddress>". "ip help-address" can only be configured for ports on layer 3 and cannot
be configured on layer 2 ports directly.
Usage Guide: When a DHCP/BootP client is connected to a VLAN1 port of the switch,
the client can only get its address from 10.16.1.0/24 instead of 10.16.2.0/24. This is
because the broadcast packet from the client will be requesting the IP address in the
same segment of the VLAN interface after VLAN interface forwarding, and the VLAN
interface IP address is 10.16.1.2/24, therefore the IP address assigned to the client will
belong to 10.16.1.0/24.
If the DHCP/BootP client wants to have an address in 10.16.2.0/24, the gateway
forwarding broadcast packets of the client must belong to 10.16.2.0/24. The connectivity
between the client gateway and the switch must be ensured for the client to get an IP
address from the 10.16.2.0/24 address pool.

11.5 DHCP Troubleshooting

If the DHCP clients cannot obtain IP addresses and other network parameters, the
following procedures can be followed when DHCP client hardware and cables have been
verified ok.
Verify the DHCP server is running, start the related DHCP server if not running.
If the DHCP clients and servers are not in the same physical network, verify the
router responsible for DHCP packet forwarding has DHCP relay function. If DHCP
relay is not available for the intermediate router, it is recommended to replace the
router or upgrade its software to one that has a DHCP relay function.
In such case, DHCP server should be examined for an address pool that is in the
same segment of the switch VLAN, such a pool should be added if not present, and
(This does not indicate ES4624-SFP/ES4626-SFP switch cannot assign IP address
for different segments, see solution 2 for details.)
In DHCP service, pools for dynamic IP allocation and manual binding are conflicting, i.e.,
if command "network-address" and "host" are run for a pool, only one of them will take
effect; furthermore, in manual binding, only one IP-MAC binding can be configured in one
pool. If multiple bindings are required, multiple manual pools can be created and IP-MAC
bindings set for each pool. New configuration in the same pool overwrites the previous
configuration.

11.5.1 Commands for Monitor and Debug

346