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LLT setup question

Created: 16 Dec 2013 • Updated: 26 Dec 2013 | 6 comments
mokkan's picture
This issue has been solved. See solution.

Hello,

It may be  a stupd question.  If we configure IP address on network card, and if we want to configure LLT over ethernet on same card, can we do it?

 

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mikebounds's picture

Yes you can configure IP address on a LLT link, but this is not recommended for high-pri (normal default) links as hi-pri heartbeats are busy so LLT traffic may effect traffic using the IP and traffic using IP may effect LLT traffic.

So better to use low-pri LLT if interface has an IP which reduces LLT traffic unless all high-pri links are lost.

Mike

UK Symantec Consultant in VCS, GCO, SF, VVR, VxAT on Solaris, AIX, HP-ux, Linux & Windows

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Gaurav Sangamnerkar's picture

Agree, you can do this but not recommended, think of an e.g where you have configured IP address on LLT links & IP is getting used for public purpose (for apps/db use). There will be connections /data traffic happening on these LLT links. Because of this busy link, if LLT traffic is not able to reach to other node & other node would assume that 1st node has gone down which may initiate unnecessary failovers.

High pri links transfer packets on LLT link every half second so LLT links are constantly used by VCS. As Mike suggested, having IP address on low pri link is OK if high pri links are good without IP

 

G

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Marianne's picture

You should have 2 dedicated NICs per cluster node for LLT comms. 
This is also referred to 'Private Network' that should only be used for cluster comms and heartbeats.

The NIC used for public network access should be the only NIC used for network traffic.
If you want to config another network interface for something like backups, you ideally need a 4th NIC in each cluster node.

Supporting Storage Foundation and VCS on Unix and Windows as well as NetBackup on Unix and Windows
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mokkan's picture

Thank you very much. When you say public network, it means it can communicate with different subnet, in this case I can only use LLT over UDP. Am I right?

Gaurav Sangamnerkar's picture

Hi,

A low pri public link will anyways have an IP address as it is being used in public network. As it will have IP address, it will work at layer 3 of OSI model & will have routing capabilities. You can use this link with any of the options TCP/UDP.

 

G

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mikebounds's picture

See comment from you other post https://www-secure.symantec.com/connect/forums/llt-over-or-udp-or-ethernet#comment-9547461 :

 

A low-pri heartbeat on a "public network" can still use LLT over Ethernet (so LLT doesn't use the IPs on the interfaces) and this is the norm.

So just because LLT link interface has an IP, LLT does NOT have to use it and in most situations it doesn't unless you NEED LLT over UDP.

Mike

 

UK Symantec Consultant in VCS, GCO, SF, VVR, VxAT on Solaris, AIX, HP-ux, Linux & Windows

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