There is a possible issue with 6.3, Intel I340AM4 network chips (i.e. IBM x3550M4 servers) with VLAN-configuration and DHCP-Relay functionality.<br />
<br />
Setup:<br />
Client1 DHCP-Server<br />
| |<br />
|-----------| |---------|<br />
|_____________|eth1.10 <- 6.3Box (x64) ->eth0|_____|<br />
<br />
Client1 is connected to the network with an untagged port<br />
eth1.10 of 6.3Box is connected with a tagged port VLAN 10<br />
6.3Box is running DHCP-relay daemon between eth0 and eth1.10<br />
eth0 is connected with an untagged port, so is the DHCP-server<br />
If client1 issues a DHCP-Request it can bo observed (tcpdump) on eth1.10 and the relayed request can be observed on eth0. The answer from the DHCP-server is also observed on both eth-IFs. A tcpdump on Client1 only shows the DHCP-Request but NO DHCP-offer...<br />
If the 6.3Box is changed to another hardware (i.e. rackserver with broadcom-based NICs) or of eth1.10 is changed to an untagged port (eth1) the DHCP-offer is received on Client1 and the IP gets assigned.<br />
The funny thing is - if Client1 gets an IP-address assigned by hand - ICMP and TCP communication works fine with the Intel-NIC based hardware ...<br />
This issue is present with the current 6.3 kernel (2.6.32-279.2.1.el6.x86_64).
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