Operating instructions

Chapter 5. Cisco Systems IGESM management and user orientation 73
Figure 5-51 Internal IP ownership issue; combined with the issues in scenario 5, scenario 6 is not
recommended
Eth1 IP 172.16.1.2
Management
Module
IGESM
Blade server on same VLAN as IGESM management VLAN interface
MM in same IP subnet as blade server
On boot-up or when restarting network drivers, server usually sends out a duplicate IP
address check (gratuitous ARP packet asking who owns its IP address). It expects no
response and would normally continue bringing up its IP address on to the network.
In this case, VLAN used by server is also carried over to the MM. The MM is hard-
programmed to respond (proxy) to all internal ARP requests on its internal Ethernet
interface for any request on its own IP subnet.
End result in this case:
BladeServer sees ARP response and assumes duplicate IP address on network. It
usually shuts down the TCP stack at that point and TCP/IP is dead for this server.
BladeCenter
ETH 0
ETH 1
MGMT
interface
VLAN X
Blade server
IP – 172.16.1.200
Blade server
using VLAN X
Blade server sends initial ARP to world
requesting info for own IP address
(essentially a duplicate IP address check)
ARP – “Who has 172.16.1.200?”
As a broadcast, this is carried on all ports on the VLAN,
including the internal facing ports toward the MM
MM sees ARP request on same IP
subnet on internal interface
Sends ARP response:
“I own 172.16.1.200 !”
1
2