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тАО05-12-2004 11:16 PM
тАО05-12-2004 11:16 PM
For decnet, I can enable the 2nd card and decnet will use both cards.
For LAT, I can create a link for the 2nd card.
For IP, I can assign a second IP address. AND I don't want to do that because my clients are unable to use it.
Is there a way to let IP use 2 cards with 1 IP address ? My IP version is 5.3 ECO 2.
And for those who know DSM/MUMPS : how will DDP use the second card ?
Solved! Go to Solution.
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тАО05-12-2004 11:28 PM
тАО05-12-2004 11:28 PM
Re: LAN failover
Thats a good one. What we have been doing is, having 2 cards configured to 2 different IPs, one for production use and the other for backup network (for carrying out backups without clogging the production network).
It would be interesting for me to see if we could have one IP assigned to 2 n/w cards and know what benefits one could get in such a configuration.
regards
Mobeen
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тАО05-12-2004 11:31 PM
тАО05-12-2004 11:31 PM
Re: LAN failover
FYI : 7.3-2 has LAN failover. 1 card can fail and the other takes over. But I don't know if this would also work if the switch behind it fails. But this is another subject.
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тАО05-13-2004 12:49 AM
тАО05-13-2004 12:49 AM
Re: LAN failover
I think you can't use same IP on two different cards; main problem is not in software but it's inside TCP/IP techinal characteristics.
When any host send a socket into network, this soccket have to reach the destination host; IP address tell to all network device where socket have to go; low level network, however doesn't use IP addres but use MAC (Medium Address Card), the hex number stored in every network device; two specific part of TCP/IP standard determine how IP address is associated to MAC and theese feature have named ARP and RARP.
If you assign same IP to 2 different NIC, some network device (mainly the routers and bridges) can be confused and can't deliver the socket.
This means, if can assign same IP to 2 different NIC you have disable one fo two devices.
I hope I can explain in simple way.
@Antoniov
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тАО05-13-2004 01:07 AM
тАО05-13-2004 01:07 AM
Re: LAN failover
Why the restrictions on upgrading?
Purely Personal Opinion
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тАО05-13-2004 01:28 AM
тАО05-13-2004 01:28 AM
Re: LAN failover
Yup, i am aware that 7.3-2 supports n/w failover, but i thought thats assuming that the 2 cards have different IP addresses and not a single IP assigned to your 2 network cards
regards
Mobeen
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тАО05-13-2004 01:37 AM
тАО05-13-2004 01:37 AM
Re: LAN failover
I don't upgrade because "on paper" all applications must approve the new system.
We need to keep the platform as stable as possible. The migration of 6.2 -> 7.3 took 2 years !!!
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тАО05-13-2004 01:46 AM
тАО05-13-2004 01:46 AM
Re: LAN failover
there is a recent thread
http://forums1.itrc.hp.com/service/forums/questionanswer.do?threadId=385987
that is mainly concerned with IP cluster alias stuff.
The thread also discusses DNS round-robin (kind of poor-mans cluster alias, or maybe more exactly: as close as Unix can get to cluster aliasing). Using this mechanism it IS possible use both cards (we are doing it, over 2 cards each of 4 nodes).
The way it works: any existing connection is to MAC address and stays where it is. After a round-robin step the service name (functional analogous to DECnet cluster adddress, but NOT the IP cluster alias!) is changed to the next MAC address, and new connections (IF using DNS, not router-cache!) get connected to the other NIC. No real load-balance, but more or less even connection-time based spread.
hth.
Jan
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тАО05-13-2004 01:54 AM
тАО05-13-2004 01:54 AM
Re: LAN failover
I found that one too. But DNS is a too big change for us. We are still using host files.
It is rather strange that since years redundant machines are sold while the network protocols are not able to use it.
Also : it would like that when the network goes down on 1 card that IP retransmits the packets on the other card.
Did someone test all this (network failure, card failure) ?
Excellent would be that in case of failure, all connections stay up and act as if the packets were lost.
Btw : how is decnet/lat reacting in case of a failure ? Is something lost ?
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тАО05-13-2004 02:20 AM
тАО05-13-2004 02:20 AM
Re: LAN failover
I understand my answer don't like you but TCP/IP suite is based on MAC (physical address of card) so, today is not possible use a secondary network card to backup a primary card :-(
Every change of card require a manual modify or else require some minutes (from 1 to max 30 minutes, depending network complex) to upgrade all ARP table of network device.
You can use DNS to solve or you have ready to accept some minutes of waiting for activation of new card.
Ortherwise don't use TCP/IP (but I think also other protocol have same limitation).
Sorry for unhappy news.
@Antoniov