Hi Guys and Gals,
I am trying to understand how L3 EtherChannel load balancing occurs when used between a multilayer switch and an ISR router.
Example config:
sw1:
int range gi0/20-24
desc linked to gi01-4 on router1
no switchport
channel-group 3 mode active
no shut
int port-channel 3
no switchport
ip address 172.16.1.1 255.255.255.252
no shut
router1:
int range gi0/1-4
desc linked to gi0/20-24
channel-group 7 mode active
no shut
int port-channel 7
ip address 172.16.1.2 255.255.255.252
no shut
I understand that if a packet with a source/destination outside of the 172.16.1.0/30 subnet is forwarded over the link it will load balance accross the links as documented.
Now my questions are as follows:
1) - If a packet is sent from router1 to sw1, it will do so over the same link every time as the load balancing uses src-dst-ip; Is this correct?
2) - Does the EtherChannel packet hashing algorithm remain constant over time (after a device reload for example, link membership change, etc), e.g. always select the same link member based on the source / destination address combination?
If the above is true, the traffic between the switch and the router heading across the EtherChannel bundle will always use the same link member, ergo inter-device traffic is not load balanced in effect?
A slight sideways step on this question would be:
3) - Has anybody successfully got load balancing working on a multilayer switch to server (host) link using a L3 EtherChannel link? I do understand that a L2 EtherChannel on a switch with SVI(s) configured would have a similar effect, and would load balance evenly if set to src-dst-ip...
4) - Am I correct in thinking that an L3 EtherChannel could only ever be used on a L3 point to point link, otherwise it would be a L2 EtherChannel?
5) - Would an L3 EtherChannel on router1 with an L2 EtherChannel configured on the switch with an SVI defined possibly work?
sw1:
vlan123
name link to router
int range gi0/20-24
desc linked to gi01-4 on router1
channel-group 3 mode active
no shut
int port-channel 3
switchport mode access
switchport access vlan 123
no shut
int vlan123
ip address 172.16.1.1 255.255.255.252
no shut
Any info / thoughts on this would be most welcomed.
James.
