Multiple ip helper-addresses: simultaneous or round robin?

Unanswered Question
Feb 18th, 2009

When more than one ip helper-address is configured on an interface, does the switch send out a unicast request to all IP helper addresses at the same time, or is there a round-robin or other sort of preferential treatment?

Thanks in advance -w

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Edison Ortiz Wed, 02/18/2009 - 17:18

The answer is:

switch send out a unicast request to all IP helper addresses at the same time

HTH,

__

Edison.

a.alekseev Thu, 02/19/2009 - 14:36

It cannot be at the same time.

First is the first, last is the last.

Some times it makes sense.

Edison Ortiz Thu, 02/19/2009 - 15:02

R3 (F0/1) <--LAN--> (F0/1) R1

R3:

interface FastEthernet0/1

description R1

ip address 192.168.13.3 255.255.255.0

ip helper-address 192.168.34.4

ip helper-address 192.168.34.5

R1:

interface FastEthernet0/1

description R3

ip address dhcp

shutdown

duplex auto

speed auto

no clns route-cache

R1(config-if)#int f0/1

R1(config-if)#no shut

R3#

00:05:22: DHCPD: setting giaddr to 192.168.13.3.

00:05:22: DHCPD: BOOTREQUEST from 0063.6973.636f.2d63.6130.302e.3166.6338.2e30.3030.362d.4661.302f.31 forwarded to 192.168.34.4.

00:05:22: DHCPD: BOOTREQUEST from 0063.6973.636f.2d63.6130.302e.3166.6338.2e30.3030.362d.4661.302f.31 forwarded to 192.168.34.5.

00:05:23: IP-EIGRP(Default-IP-Routing-Table:1): Neighbor 0.0.0.0 not on common subnet for FastEthernet0/1

00:05:25: DHCPD: setting giaddr to 192.168.13.3.

00:05:25: DHCPD: BOOTREQUEST from 0063.6973.636f.2d63.6130.302e.3166.6338.2e30.3030.362d.4661.302f.31 forwarded to 192.168.34.4.

00:05:25: DHCPD: BOOTREQUEST from 0063.6973.636f.2d63.6130.302e.3166.6338.2e30.3030.362d.4661.302f.31 forwarded to 192.168.34.5.

00:05:27: DHCPD: setting giaddr to 192.168.13.3.

00:05:27: DHCPD: BOOTREQUEST from 0063.6973.636f.2d63.6130.302e.3166.6338.2e30.3030.362d.4661.302f.31 forwarded to 192.168.34.4.

00:05:27: DHCPD: BOOTREQUEST from 0063.6973.636f.2d63.6130.302e.3166.6338.2e30.3030.362d.4661.302f.31 forwarded to 192.168.34.5.

HTH,

__

Edison.

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