Changing SG LANs

[Roberto Volsa]

Hello
i need to change a networl connection used by SG (release 11.16):
the actual connection is that HB (private lan) uses a switch, the new connection required is a direct connection via cross-cable.

Ths SG configuration thus is not changed.
When i remove the switch connection i read on both nodes the "lan failed" message, but wheh the cross cable is connected the lan is not recovered, also if the linkloop between the two cards works perfectly.

Is there something i have missed?
thanks in advance
RV

[Mike Shilladay]

Hi Roberto,

The use of a crossover cable is not officially supported in SG clusters. It will probabaly do what you require.

Suggest a small hub to get around the problem.

Mike.

[Roberto Volsa]

Thans Mike,
i know the problem related to the cross cable, this solution is required only temporary in order to avoid the actual switch.

Best regards
RV

[melvyn burnard]

did you do the change while the cluster was up?
You may need to rerset the lan ports with lanadmin
also, you would have to make sure that autonegotiate was turned off for these .
I attach a statement from HP regarding support of cross over cables:

We often get questions asking whether Crossover cables are supported for use in a Serviceguard cluster. The short answer is YES, but there are some important issues that you should be aware of:

This solution only works in a two node cluster. There is no way to have a Standby LAN card when using a Crossover LAN cable, so it is not possible to use SG local LAN failover.

When either LAN card fails, or the crossover cable is disconnected, both LAN cards go down. This is because the electrical signals necessary for the cards to determine that a valid LAN connection exists are not present. The result is that since both nodes appear to have a bad LAN card, Serviceguard may TOC the wrong node. If a hub was used between the two LAN cards, then the hub would provide the electrical signals to the other card, allowing it to stay up.

On multi-speed cards, such as 10/100Base-T, the cards must negotiate which speed will be used when the system boots up. If only one system is booted and the remote system is down, then the negotiation will fail, and the card will not be enabled at all. So when the second node eventually comes up, it's LAN will also be down. If a hub is used, then the negotiation will succeed, so the LAN cards will come up at bootup, even if only one node is running.
It may be possible to force some multi-speed LAN cards to bypass the negotiation at bootup and to use a predetermined fixed speed. If this is possible, then would allow the two systems to boot up at different times and still use the Crossover cable connected LAN cards once they are both booted up.

Since both cards may go down when there is a failure when a Crossover cable is used, it can be difficult to determine where the problem lies. Another problem using Crossover cables is that if they are not properly labeled, they may accidently be used in situations where they will not work.
For the reasons listed above, HP does not recommend using Crossover cables for Serviceguard configurations. However, they are still supported as long as you are willing to accept the above limitations. Using a Crossover cables is cheaper than using a hub, but it compromises the HA solution.