Port-channel not getting desirable aggregated bandwidth

[Lawrence Chia Chao Xian]

Hey Guys,

I got 1 issue.

Topology:

LAN - FW - 3750G (A) - (4 x 100Mb links aggregated into 1 port-channel) 3750 (B) - Router - Internet

I  am doing source dest IP loadbalancing on 3750G (L2) at A and  the Service Provider is running source destination IP loadbalancing too on  the 3750 (L2) at B.

I  am not able to get an aggregated bandwidth of more than 100Mb upload on  the port-channel at the 3750G at A, when various source from the  Internet is doing a download from my server behind LAN.

Is there anything that be done to improve the throughput?

[ankugarg]

Hi Lawrence,

just to be clear about the problem,are you running source dest IP loadbalancing or mac address load balancing..In another thread you are saying that you are running source mac load balancing...Low bandwidth is expected in that case as i explained there...We need to troubleshoot more if you are running source dest IP load balancing.

[Lawrence Chia Chao Xian]

Hi Ankur,

I was running source mac load balancing and the SP was running dest mac load balancing. They have since advised us to use source-dest IP instead.

[Edison Ortiz]

In order for the switches to load-balance the port-channel based on IP, they need to have the IP information.

Neither switch has the internet table hence the src and dst is based on the mac-address of the directly connected device or the IP address of the directly connected device which is the same. Port-channel is hashing to the same physical interface.

If you want more bandwidth, you have to allow more routes in the 3750B switch.

Keep in mind, there is a limitation of routes on which the 3750 can support. You are looking at up to 11k Unicast routes.

Regards,

Edison

[Lawrence Chia Chao Xian]

Hi Edison,

The switches are running L2. So in this case, they will fall back to the dest mac load-balancing?

[ankugarg]

Hi Edison,

Just want to have follow up question on your first reply...If the switch is L2,can it do load balancing based on IPs.or it will fall back to mac addresses.Thanks.

[ankugarg]

Some extra bit of info which might be useful--You can use the command "sh interfaces counters etherchannel",which tell total packets going through port channel,and distribution between various ports in that port channel...You can check if only one of the physical interface is used or all are getting used.

4-mem-stack#sh interfaces counters etherchannel

Port            InOctets    InUcastPkts    InMcastPkts    InBcastPkts

Po1             13278414            735          29243              0

Gi1/0/1          2598013            316           6373              0

Gi3/0/1         10693013            419          22912              0

Po2             12650641              0          29261              0

Gi1/0/2         12373522              0          27655              0

Gi3/0/2           285810              0           1651              0

Po4                    0              0              0              0

[Lawrence Chia Chao Xian]

Hi Ankur,

The output result is as below, seems like traffic are tranversing on all ports.

show interfaces counters etherchannel

Port            InOctets   InUcastPkts   InMcastPkts   InBcastPkts

Po1          75387124586     118437633        824973         13414

Gi1/0/7      38465013917      62792609        284628         16551

Gi1/0/8      23111368103      17557169        462245            94

Gi1/0/9      11892707225      19222121         21989          1929

Gi1/0/10      1684922672       8659179          8537             0

Port           OutOctets  OutUcastPkts  OutMcastPkts  OutBcastPkts

Po1         205239821953     169908718         56641          5248

Gi1/0/7       4126310711       8299118         14139           724

Gi1/0/8     111692349227      95559233         16397          4621

Gi1/0/9      66153093922      50716674         15730           272

Gi1/0/10      4457641077       2938790           934             0

[ankugarg]

Hmm..yes...r u sure there are no other bottlenecks in the network.

[Lawrence Chia Chao Xian]

Hi Ankur,

I was able to get the desirable throughput from my switch toward the server on my LAN segment. Guess I have to check back with the SP.

[Edison Ortiz]

What did you do to get the desirable throughput?

[Lawrence Chia Chao Xian]

I did an access port to the 3750G (A) and was able to get the desirable download speed from the client to the server at LAN.