Comments inline...... > Once you;ve done this, when a packet arrives at the DHCP server > with a > giaddr of > P, the DHCP server now knows that P and S1, S2, and S3 are all > related. > The DHCP > server uses this, and any configurations the operator has > provided > to help select the appropriate scope (subnet) and thus IP for > this > device.
I understand the logic of tying the secondary scopes to the primary at ehe DHCP side, however if the giaddr always reflects the primary subnet, how the the DHCP server ever know to hand out addrs from the other secondary scopes? > Note, above I indicated that the primary address is *usually* > the > giaddr. > Two caveats to this: > > * Cisco changed how the relay helpering works in some IOS > revs-- in some > 11.x > or 12.x revs, the giaddr can cycle through all gateway addresses > assigned on the > helpering interface. That is, when a packet gets helpered, the > router > will initially > insert the P address as the giaddr. If the DHCP server does not > respond, and > the router has helpered 3-4 DISCOVERs on behalf of a source, > the 5-8th > DHCP DISCOVER > packets will get helpered using a giaddr of S1. This repeats > 3-4 times, > and if no > DHCP response is received, S2 is used as the next giaddr. This "feature" you describe sounds pretty worthless. If the giaddr is always from P, and rotates through S1, S2, S3, etc when the DHCP server doesn't respond, then unless your DHCP server is down or all IPs have been allotted for subnet P, then the DHCP request will always result in an IP from the scope for P. Mike W. Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=35612&t=35539 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
