IP address assignment via local pooling

[sfchewtac]

dear fellow;

I am a bit confused here regarding the sequencing of ip assignment via local pooling. My questions are:

1)will the ip address be assigned in sequence to remote users?

2)How does caching actually work via local pooling?

3)if the same user disconnected and reconnected again, will it be reassigned the same IP again?

Thanks,

Sam

[Richard Burts]

Sam

The context of your question is not clear to me. Are you asking about address pool as in the router configured as a DHCP server, or address pool configured for the router processing dial access and assigning addresses, or address pool configured as part of terminating VPN remote access sessions and assigning addresses?

From experience with routers with dial access I observe that they do manage the address pool and do maintain some type of cache so that if a user has been connected and received an address and if they reconnect within some period of time (I am not at all clear what the time period is) that they generally get assigned the same address. With DHCP when the lease expires and a user reconnects they will frequently get the same address assigned. But depending on the volitility of the DHCP pool it is also possible that some other user might have gotten assigned that address before the original user reconnects and requests an address.

HTH

Rick

[Pavel Bykov]

According to DHCP standard:

1. Addresses are assigned in sequence

2. Caching? Of IP addresses? DHCP allocates memory, and remembers all assigned addresses there, and their expiration. DHCP checks the presence of an address before issuing it, if DHCP is restarted or the pool is cleared.

3. It should, but it depends on lease expiration. I believe Cisco has expiration of one day by default. Then the station has to re-request the address. So, if the station is not turned off for too long, it will get the same address (DHCP decides this based on station's MAC). But if the station is off for several days, and DHCP allocates the address to someone else, station will get a different address.

Use reservation if you want station to always get the same IP, and don't want that IP to be assigned to anyone else.

More here:

http://www.cisco.com/en/US/customer/tech/tk648/tk361/technologies_configuration_example09186a0080094a52.shtml

[sdesteuben]

on my asa5505 if i disconnect my client vpn the pool issues me the next address. as was stated already it seems to be an issue of the lease. with the DHCP pool it works a bit diffrent. if i release and renew i will get the same address. if i turn off and turn on the same result will happen provided nobody else looks for an address, and provided time is not long b/t restart