Nexus - port-channel load balancing

Port-channel load balancing is a global command or interface command in Nexus switch?
Thanks,
Manu

Hi,
It's a global command; port-channel load-balance ethernet.
You can find details in the Configuring Load Balancing Using Port Channels section of the Nexus 5500 Series NX-OS Interfaces Configuration Guide.
Regards

Similar Messages

Nexus port channel load balance

Hi
I just want to clarify one setting for the port channel load balance on Nexus 6k switch. If I use the load balance option source-dest-ip-only, will following four converstions be load balanced?
10.10.10.1 -> 192.168.1.1
10.10.10.2 -> 192.168.1.1
10.10.10.1 -> 192.168.1.1
10.10.10.1 -> 192.168.1.2
Thanks. Leo

Hi Leo,
I think there may be typo in your question as I only see three conversations and not four. That aside I've not seen the Nexus port-channel load balancing sufficiently well documented to be able to give you the exact answer.
In their configuration guides Cisco only include the following statement:
Cisco NX-OS load balances traffic across all operational interfaces in a port channel by reducing part of the binary pattern formed from the addresses in the frame to a numerical value that selects one of the links in the channel.
There is other documentation that states the load balancing algorithm uses a CRC-8 based polynomial, but as we don't know exactly which parts of the frame are used in the calculation, I don't see it's possible to calculate the answer and so derive the link that will be used for a given conversation.
While I've not seen full documentation regarding the science used in the calculation, what Cisco have done is provide a command on the switch CLI that will allow you to determine which link of a port-channel will be used.
If you run the command show port-channel load-balance forwarding-path interface port-channel vlan src-ip dst-ip then one of the parts of the output is the member link of the port-channel that will be used for that flow.
You can find full details of the options for the show port-channel load-balance command in the command reference.
One other point to remember is that the load balancing across a port-channel is unidirectional, and the hashing might be completely different for the return flow of a conversation. For example it is entirely possible that traffic from A to B could use one link of a port-channel, while the return traffic from B to A for the same conversation could use a different link.
In general I would use the source-dest-port option for load balancing on the Nexus switches as this will obviously include the Layer-4 port numbers in the calculation, and so give you a better distribution of flows across all member links.
Regards

Nexus 6K: Port-Channel Load-Balance

Hi all,
I configured "port-channel load-balance ethernet source-dest-mac" on Nexus 6001. But when I use "show run all | in load-balance", it displays module 1 and module 2 are still using source-dest-ip for port-channel load-balance. And for command "show port-channel load-balance" and "show port-channel load-balance forwarding-path interface", it still shows switch using MAC for hash algorithm. The NXOS is 6.0(2)N1(2a).
Does anybody know:
- What is the function of "port-channel load-balance ethernet source-dest-ip module" and in which situation this command will be effective?
- It shows "port-channel load-balance ethernet source-dest-ip module" command for both module 1 and 2. Module 1 is N6K Supervisor and module 2 is 4xQSFP Ethernet Module. Is it possible to set different load-balance algorithm  to these 2 modules?
# show run all | in load-balance
port-channel load-balance ethernet source-dest-mac
port-channel load-balance ethernet source-dest-ip module 1
port-channel load-balance ethernet source-dest-ip module 2
# show port-channel load-balance
Port Channel Load-Balancing Configuration:
System: source-dest-mac
Port Channel Load-Balancing Addresses Used Per-Protocol:
Non-IP: source-dest-mac
IP: source-dest-mac
# show port-channel load-balance forwarding-path interface port-channel 30 vlan 150 src-ip 172.25.228.6 dst-ip 172.25.226.97
Missing params will be substituted by 0's.
Load-balance Algorithm on switch: source-dest-mac
crc_hash: 977 Polynomial: CRC10b        Outgoing port id Ethernet1/2
Param(s) used to calculate load-balance:
        seed: 0x701
        dst-mac: 0000.0000.0000
        src-mac: 0000.0000.0000
# show module
Mod Ports Module-Type                         Model                  Status
1   48    Norcal 64 Supervisor                N6K-C6001-64P-SUP      active *
2   10    Nexus 4xQSFP Ethernet Module        N6K-C6001-M4Q          ok
Mod Sw              Hw      World-Wide-Name(s) (WWN)
1    6.0(2)N2(3)     1.0     --
2    6.0(2)N2(3)     1.0     --

Hi all,
I configured "port-channel load-balance ethernet source-dest-mac" on Nexus 6001. But when I use "show run all | in load-balance", it displays module 1 and module 2 are still using source-dest-ip for port-channel load-balance. And for command "show port-channel load-balance" and "show port-channel load-balance forwarding-path interface", it still shows switch using MAC for hash algorithm. The NXOS is 6.0(2)N1(2a).
Does anybody know:
- What is the function of "port-channel load-balance ethernet source-dest-ip module" and in which situation this command will be effective?
- It shows "port-channel load-balance ethernet source-dest-ip module" command for both module 1 and 2. Module 1 is N6K Supervisor and module 2 is 4xQSFP Ethernet Module. Is it possible to set different load-balance algorithm  to these 2 modules?
# show run all | in load-balance
port-channel load-balance ethernet source-dest-mac
port-channel load-balance ethernet source-dest-ip module 1
port-channel load-balance ethernet source-dest-ip module 2
# show port-channel load-balance
Port Channel Load-Balancing Configuration:
System: source-dest-mac
Port Channel Load-Balancing Addresses Used Per-Protocol:
Non-IP: source-dest-mac
IP: source-dest-mac
# show port-channel load-balance forwarding-path interface port-channel 30 vlan 150 src-ip 172.25.228.6 dst-ip 172.25.226.97
Missing params will be substituted by 0's.
Load-balance Algorithm on switch: source-dest-mac
crc_hash: 977 Polynomial: CRC10b        Outgoing port id Ethernet1/2
Param(s) used to calculate load-balance:
        seed: 0x701
        dst-mac: 0000.0000.0000
        src-mac: 0000.0000.0000
# show module
Mod Ports Module-Type                         Model                  Status
1   48    Norcal 64 Supervisor                N6K-C6001-64P-SUP      active *
2   10    Nexus 4xQSFP Ethernet Module        N6K-C6001-M4Q          ok
Mod Sw              Hw      World-Wide-Name(s) (WWN)
1    6.0(2)N2(3)     1.0     --
2    6.0(2)N2(3)     1.0     --

Port Channel Load-Balancing Algorithm (North Bound)

I'm trying to figure out what the load balancing algorithm for the 6100 and 6200 FIs for the Northbound connections. I can't find any documentation on how to change it.
The Nexus 7000s use an 8-bit hash, making it very easy to do something other than 2, 4, or 8 link port channel and get even (at least algorithmically) distribution.
Catalyst switches (not sure about Sup2T though) would use a 1, 2, or 3-bit index, which would skew traffic algorthmically if you used a non-power of 2.
Looking at the 5K documentation, it seems to use the Catalyst style (though haven't been able to confirm). My guess is that whatever is used for the 5Ks is used for the 6100/6200.
Design wise, this would mean you would want to use powers of 2 for your NB uplinks.

Hello Tony,
On UCS FI, it uses " sr-cdest-ip " as the load balancing algorithm and uses 8 parameters for hashing
6248-01-B(nxos)# sh port-channel load-balance
Port Channel Load-Balancing Configuration:
System: source-dest-ip
Port Channel Load-Balancing Addresses Used Per-Protocol:
Non-IP: source-dest-mac
IP: source-dest-ip source-dest-mac
6248-01-B(nxos)# show platform fwm info pc port-channel 1
dump pc info: if_index 369098752 dump_all 0 verbose 1
Po1: state 0x0 #pifs 1 fwimpd ctx 0x9666c1c
Po1: hash params - l2_da 1 l2_sa 1 l3_da 1 l3_sa 1
Po1: hash params - l4_da 1 l4_sa 1 xor_sa_da 1 hash_elect 1
I could not find an option to change these values.
Padma

Cisco MDS Port channel load balancing

A customer recently asked an interesting question about exchange based load balancing on an FC port channel. The platform is UCS with an 8 and 16 port channel per fabric interconnect on two separate UCS domains. The application is Oracles data warehousing which has been known to saturate 4 x 8gb fc links. Since the balancing method is exchange based what constitutes the start and end of an exchange? We are trying to avoid a condition where and intense read write conversation locks to a single link in the port channel and not spread across 8/16 links. Where can I find more information about exchange based routing protocol or how should I go about managing extreme io in a converged infrastructure.

The default loadbalance method on FI and MDS is src-dst-ox-id based. Note that loadbalancing is done by a device on *outgoing traffic*. FI and MDS do not have to negotiate anything here. Technically, one device can do src-dst-id based while the other can use src-dst-ox-id. However, in your case there is no reason for such a change.
As I wrote before, If all of the links in the port-channel are touching the max capacity, you should recommend your customer to increase links in the bundle (max 16) or upgrade to 16G links. If few of the links are heavily utilized while other links in the same port-channel are under utilized, you may want to check the application or HBA for capability of breaking down the large reads/writes under smaller exchanges. If no traffic is going on few of the links at all, then I would suspect UCS to FI pinning as well.

Port channel Load balancing in Storage VDC

Hi i am not able to find how to check PO load balancing for storage VDC, although i know by default for FCoE traffic on storage vdc it is OXID but whether it is src-dst l4port or src-dst ipl4port.

Hi,
From "Nexus 5500 to Nexus 7000 Multi-Hop FCoE Configuration Example" ,
Note: On Nexus 7000, by default the source-destination-oxid load balancing mechanism is used for FCoE traffic.
So let's see what is the default load balancing mechanism in Nexus 7000,
From "Nexus 7000 interface configuration guide" ,
The default load-balancing mode for Layer 3 interfaces is the source and destination IP address, and the default load-balancing mode for non-IP interfaces is the source and destination MAC address.
Which means src-dst ip.
So what I think is you need to have src-dst ip in default VDC for OXID load balancing in Nexus 7000.

3750X Port-Channel Load-Blanace method

I have a 3750X and I'm wondering what would be the best Port-Channel Load-Balancing method would be for my network.
switch(config)#port load ?
dst-ip       Dst IP Addr
dst-mac      Dst Mac Addr
src-dst-ip   Src XOR Dst IP Addr
src-dst-mac Src XOR Dst Mac Addr
src-ip       Src IP Addr
src-mac      Src Mac Addr
We have a few Layer 3 VLANs: Default, Servers, Clients, and Guests.
Some of our servers are LACP bundled.
So it would be mainly clients on the one layer 3 VLAN accessing the server on the other layer 3 VLAN.
We also have a few smaller switches that are trunked and LACP bundled back to the core 3750X.
Can anyone suggest which Load-Balancing method would be best for our situation?
Thanks!

The default load balancing method on the 3750 series is based on source-MAC address. This usually works fine in most cases. If you change it to something different than this, it will affect all your port-channels in that switch.
HTH

How can ftp service on non-standard port be load balanced using Cisco ACE.

How can ftp service on non-standard port be load balanced using Cisco ACE.For example ftp service required on tcp 2000 port

Hi Samarjit,
you can do this by specifying the port number in the class map that you create . Please find the below mentioend config guide where you can specify the tcp/udp port , range or ports or even the wild card to match the port.
http://www.cisco.com/en/US/docs/interfaces_modules/services_modules/ace/v3.00_A1/configuration/administration/guide/mapolcy.html#wp1318826
Regards
Abijith

Two gateways, port-based load balancing

Hello,
I have a simple question on Mac OS X Leopard/SL Server regarding the use of 2 distinct internet connections on a single LAN.
Gateway #1 : 10.0.1.1 (delivering IPs) - 18 mbps
Gateway #2 : 10.0.1.254 - 4 mbps
Any computer accessing the network is delivered an IP by the DHCP server (10.0.1.1), thus uses #1 as of main gateway.
The main server (10.0.1.16) is running DNS services and a Squid proxy-cache.
Now, is it possible to set all the computers that connect to the network up so that they use the main server as of main gateway and see their requests redirected to #1 or #2 according to the port in use ?
For example:
mail,http,https,jabber -> #1
skype,rtsp,... -> #2
Thank you very much for your help
Tha
Message was edited by: Kwintin

is it possible to set all the computers that connect to the network up so that they use the main server as of main gateway and see their requests redirected to #1 or #2 according to the port in use ?
No. routing is based on destination IP address, not port.
Therefore each client will send all traffic for a specific address to a specific router address. It doesn't matter whether it's talking HTTP, SMTP, IMAP, POP, AIM, or any other protocol - any traffic for that IP will go to the same router.
You have three ways of getting around this.
One is to install a router that supports dual WAN connections. Point all internal clients to the LAN address of the router and let it do the work of routing the traffic as needed, based on its routing policies (routers may be able to route based on port).
Option two is to setup a proxy server for specific services - for example you could setup a HTTP/HTTPS proxy server on a machine that has router #1 as its default gateway and configure the clients to talk to router #2. All traffic on the clients will go over router #2 except the proxied traffic which will go to the proxy and then out via router #1.
This is relatively simple to setup, but is limited to traffic that can be easily proxied (e.g. that probably excludes email).
The third option is static routing. Look at the servers each machine is contacting and setup static routes for the smaller set of addresses. For example, if you're only splitting off traffic to Skype's servers then set each client with a default route of router #1, and static routes to Skype's server to router #2. Now all traffic except that to Skype will use router #1.
This is really only viable if you have a relatively small number of destination addresses you're trying to divert. That's why it works well for Skype (single server address), but wouldn't work well for something more generic such as 'web traffic' since you cannot predict which web servers (and therefore which IP addresses) need static routes.
Of the three options, only option #1 will cover all protocols for all clients, but it's also the only option that costs $$s if your current router doesn't support multiple WAN interfaces.

Load-balancing Algorithm for NX-OS Port Channels

Hi, all
I do not understand description of port-channel load-balance ethernet command.
switch(config)# port-channel load-balance ethernet ?
destination-ip         Destination IP address
destination-mac        Destination MAC address
destination-port       Destination TCP/UDP port
source-dest-ip         Source & Destination IP address (includes l2)
source-dest-ip-only    Source & Destination IP addresses only
source-dest-mac        Source & Destination MAC address
source-dest-port       Source & Destination TCP/UDP port (includes l2 and l3)
source-dest-port-only Source & Destination TCP/UDP port only
source-ip              Source IP address
source-mac             Source MAC address
source-port            Source TCP/UDP port
Please tell me what the following descriptions mean.
Source & Destination IP address (includes l2)
Source & Destination TCP/UDP port (includes l2 and l3)
What are the meaning of "includes l2" and "includes l2 and l3" ?
Thank you for your cooperation in advance.

Hi Satoru,
On the Nexus 5000/6000 platforms, all FEXs will inherit the global hashing algorithm from the parent device.
On the Nexus 7000 platform, hashing algorithms can be assigned on a per FEX basis (all load balancing changes must be made from the Admin VDC):
N7K-A(config)# port-channel load-balance src-dst ip-l4port fex 134
Any FEX without a hashing algorithm configured with inherit the global hash. Making changes to the modular/global hash will not alter FEX specific hashing algorithms.
To verify the configuration applied you can use this command:
N5K_A# show port-channel load-balance
On the Nexus 7000, the per FEX algorithm can be checked by appending the ‘fex <#>’ to the end of the command in the Admin VDC or the FEX’s respective VDC:
N7K-A(config)# show port-channel load-balance fex 134
Regards,
Richard

OSPF load balancing across multiple port channels

I have googled/searched for this everywhere but haven't been able to find a solution. Forgive me if I leave something out but I will try to convey all relevant information. Hopefully someone can provide some insight and many thanks in advance.
I have three switches (A, B, and C) that are all running OSPF and LACP port channelling among themselves on a production network. Each port channel interface contains two physical interfaces and trunks a single vlan (so a vlan connecting each switch over a port channel). OSPF is running on each vlan interface.
Switch A - ME3600
Switch B - 3550
Switch C - 3560G
This is just a small part of a much larger topology. This part forms a triangle, if you will, where A is the source and C is the destination. A and C connect directly via a port channel and are OSPF neighbors. A and B connect directly via a port channel and are OSPF neighbors. B and C connect directly via a port channel and are OSPF neighbors. Currently, all traffic from A to C traverses B. I would like to load balance traffic sourced from A with a destination of C on the direct link and on the links through B. If all traffic is passed through B, traffic is evenly split on the two interfaces on the port channel. If all traffic is pushed onto the direct A-C link, traffic is evenly balanced on the two interfaces on that port channel. If OSPF load balancing is configured on the two vlans from A (so A-C and A-B), the traffic is divided to each port channel but only one port on each port channel is utilized while the other one passes nothing. So half of each port channel remains unused. The port channel on B-C continues to load balance, evenly splitting the traffic received from half of the port channel from A.
A and C port channel load balancing is configured for src-dst-ip. B is a 3550 and does not have this option, so it is set to src-mac.
Relevant configuration:
Switch A:
interface Port-channel1
description Link to B
port-type nni
switchport trunk allowed vlan 11
switchport mode trunk
interface Vlan11
ip address x.x.x.134 255.255.255.254
interface Port-channel3
description Link to C
port-type nni
switchport trunk allowed vlan 10
switchport mode trunk
interface Vlan10
ip address x.x.x.152 255.255.255.254
Switch B:
interface Port-channel1
description Link to A
switchport trunk encapsulation dot1q
switchport trunk allowed vlan 11
switchport mode trunk
interface Vlan11
ip address x.x.x.135 255.255.255.254
interface Port-channel2
description Link to C
switchport trunk encapsulation dot1q
switchport trunk allowed vlan 12
switchport mode trunk
interface Vlan12
ip address x.x.x.186 255.255.255.254
Switch C:
interface Port-channel1
description Link to B
switchport trunk encapsulation dot1q
switchport trunk allowed vlan 12
switchport mode trunk
interface Vlan12
ip address x.x.x.187 255.255.255.254
interface Port-channel3
description Link to A
switchport trunk encapsulation dot1q
switchport trunk allowed vlan 10
switchport mode trunk
interface Vlan10
ip address x.x.x.153 255.255.255.254

This is more FYI. 10.82.4.0/24 is a subnet on switch C. The path to it is split across vlans 10 and 11 but once it hits the port channel interfaces only one side of each is chosen. I'd like to avoid creating more vlan interfaces but right now that appears to be the only way to load balance equally across the four interfaces out of switch A.
ME3600#sh ip route 10.82.4.0
Routing entry for 10.82.4.0/24
Known via "ospf 1", distance 110, metric 154, type extern 1
Last update from x.x.x.153 on Vlan10, 01:20:46 ago
Routing Descriptor Blocks:
x.x.x.153, from 10.82.15.1, 01:20:46 ago, via Vlan10
Route metric is 154, traffic share count is 1
* x.x.x.135, from 10.82.15.1, 01:20:46 ago, via Vlan11
Route metric is 154, traffic share count is 1
ME3600#sh ip cef 10.82.4.0
10.82.4.0/24
nexthop x.x.x.135 Vlan11
nexthop x.x.x.153 Vlan10
ME3600#sh ip cef 10.82.4.0 internal
10.82.4.0/24, epoch 0, RIB[I], refcount 5, per-destination sharing
sources: RIB
ifnums:
Vlan10(1157): x.x.x.153
Vlan11(1192): x.x.x.135
path 093DBC20, path list 0937412C, share 1/1, type attached nexthop, for IPv4
nexthop x.x.x.135 Vlan11, adjacency IP adj out of Vlan11, addr x.x.x.135 08EE7560
path 093DC204, path list 0937412C, share 1/1, type attached nexthop, for IPv4
nexthop x.x.x.153 Vlan10, adjacency IP adj out of Vlan10, addr x.x.x.153 093A4E60
output chain:
loadinfo 088225C0, per-session, 2 choices, flags 0003, 88 locks
flags: Per-session, for-rx-IPv4
16 hash buckets
< 0 > IP adj out of Vlan11, addr x.x.x.135 08EE7560
< 1 > IP adj out of Vlan10, addr x.x.x.153 093A4E60
< 2 > IP adj out of Vlan11, addr x.x.x.135 08EE7560
< 3 > IP adj out of Vlan10, addr x.x.x.153 093A4E60
< 4 > IP adj out of Vlan11, addr x.x.x.135 08EE7560
< 5 > IP adj out of Vlan10, addr x.x.x.153 093A4E60
< 6 > IP adj out of Vlan11, addr x.x.x.135 08EE7560
< 7 > IP adj out of Vlan10, addr x.x.x.153 093A4E60
< 8 > IP adj out of Vlan11, addr x.x.x.135 08EE7560
< 9 > IP adj out of Vlan10, addr x.x.x.153 093A4E60
<10 > IP adj out of Vlan11, addr x.x.x.135 08EE7560
<11 > IP adj out of Vlan10, addr x.x.x.153 093A4E60
<12 > IP adj out of Vlan11, addr x.x.x.135 08EE7560
<13 > IP adj out of Vlan10, addr x.x.x.153 093A4E60
<14 > IP adj out of Vlan11, addr x.x.x.135 08EE7560
<15 > IP adj out of Vlan10, addr x.x.x.153 093A4E60
Subblocks:
None

Nexus 1000v load balancing policy

what load balancing policy is used for the 1000v?
looks like the default is
port-channel load-balance ethernet source-mac
when shuld another policy be used?
dest-ip-port              Destination IP address and L4 port
dest-ip-port-vlan         Destination IP address, L4 port and VLAN
destination-ip-vlan       Destination IP address and VLAN
destination-mac           Destination MAC address
destination-port          Destination L4 port
source-dest-ip-port       Source & Destination IP address and L4 port
source-dest-ip-port-vlan Source & Destination IP address, L4 port and VLAN
source-dest-ip-vlan       Source & Destination IP address and VLAN
source-dest-mac           Source & Destination MAC address
source-dest-port          Source & Destination L4 port
source-ip-port            Source IP address and L4 port
source-ip-port-vlan       Source IP address, L4 port and VLAN
source-ip-vlan            Source IP address and VLAN
source-mac                Source MAC address
source-port               Source L4 port
source-virtual-port-id    Source Virtual Port Id
vlan-only                 VLAN only

By the way,
Sample config to enable persistence rebalance for your existing config is as follows:
parameter-map type http persist
persistence-rebalance
policy-map multi-match VLAN300_LAYER4_POLICY
class VIP_WEBSITE_HTTPS
         appl-parameter http advanced-options persist
Joel

N5K: PortChannel & Load Balancing

Hello All,
I've configured port-channel for my backup servers and also applied load balancing on the switch (NEXUS 5548 with 2248 FEX). The server is configured with NIC teaming and is set on auto, which negotiates to use 802.3ad for the channel.
All seems to be working fine however the ports do not seem to be balancing the traffic when transmitting unicast traffic as shown from below N5K output:
ChanId      Port     Rx-Ucst Tx-Ucst Rx-Mcst     Tx-Mcst   Rx-Bcst Tx-Bcst
20   Eth102/1/6 52.61% 99.99%    49.45% 63.29% 93.55% 51.27%
20   Eth102/1/5 47.38%   0.00%     50.54% 36.70%   6.44%    48.72%
21   Eth102/1/33 51.25% 99.99% 49.92% 63.01%   15.51%   51.40%
21   Eth102/1/29 48.74% 0.00% 50.07% 36.98%     84.48%   48.59%
The above shows the server is receiving traffic only on one port and not balancing it on another. Server is WIn 2008 R2. These are 1 Gig links with PO are 2 Gig, the backup server needs the 2 Gig but somehow it doesnt seem to utilize the port-channel for incoming traffic.
Currently the load balancing on the N5K platform is set as follows:
N5K# show port-channel load-balance
Port Channel Load-Balancing Configuration:
System: source-dest-port
Port Channel Load-Balancing Addresses Used Per-Protocol:
Non-IP: source-dest-mac
IP: source-dest-port source-dest-ip source-dest-mac
My question here is can i load balance the Tx-Ucst to both ports?
Is there some other way I can utilize both NIC cards on the server to receive traffic?
Any help would be much appreciated.
Thank you.
Regards,
Adnan M F

Adnan,
You seem to be using the recommended hashing algorithm. I would use the "show port-channel load-balance forwarding-path" command to verify that your traffic would actually load balance. Because you mention these are backup servers, I'm concerned there may not be enough entropy in the packets to load balance as you'd like.
example :
show port-channel load-balance forwarding-path interface port-channel 301 vlan 1 src-ip 1.1.1.1 l4-dst-port 80 dst-ip 2.2.2.2 l4-src-port 20000
Missing params will be substituted by 0's.
Load-balance Algorithm on switch: source-dest-ip
crc8_hash: Not Used     Outgoing port id: Ethernet1/9
Param(s) used to calculate load-balance (Unknown unicast, multicast and broadcas
t packets):
        dst-mac: 0000.0000.0000
        vlan id: 1
If the "show port-channel load-balance forwarding-path" commands shows that your traffic should transmit out eth102/1/5 or eth102/1/29, then it's possible you are having bug issues. There are known bugs that were fixed in 5.2(9) and 6.1(4) that affect load balancing.

IOS to NXOS VPC PORT CHANNEL

Hello
I have a pair of Nexus 5K's in a VPC domain and some 2960's as VPC members, with a port channel to the domain.
Topology is as follows:
5K1 and 5K2 in VPC domain
VPC from 5K1 and 5K2 to 2960
2960 has gi0/1 and gi0/2 in 1 port channel
gi0/1 to 5k1, gi0/2 to 5k2
I know that what I am going to ask may be totally against the purpose of VPC, but, I am looking for a way to favour gi0/1 for traffic, rather than load balancing over gi0/1 and gi0/2. The reaon for this is that I would like to benefit from the lack of loop that VPC provides, but would also like to have a primary and secondary link as the majority of traffic should actually go via 5K1, rather than 5K2.
Any suggestions welcome.
Many thanks in advance
Anthony

Hi Anthony,
The Cisco NX-OS software load balances traffic across all operational interfaces in a portchannel by hashing the addresses in the frame to a numerical value that selects one of the links in the channel. Port channels provide load balancing by default. Port-channel load-balancing uses MAC addresses, IP addresses, or Layer 4 port numbers to select the link. Port-channel load balancing uses either source or destination addresses or ports, or both source and destination addresses or ports.
You can configure the load-balancing mode to apply to all port channels that are configured on the entire device or on specified modules. The per-module configuration takes precedence over the load-balancing configuration for the entire device. You can configure one load-balancing mode for the entire device, a different mode for specified
modules, and another mode for the other specified modules. You cannot configure the load-balancing method per port channel.
You can configure the type of load-balancing algorithm used. You can choose the load-balancing algorithm that determines which member port to select for egress traffic by looking at the fields in the frame.
Note: The default load-balancing mode for Layer 3 interfaces is the source and destination IP address, and the default load-balancing mode for non-IP interfaces is the source and destination MAC address.
From the config mode you can try different load-balacing method ,
port-channel load-balance {dest-ip-port | dest-ip-port-vlan |
destination-ip-vlan | destination-mac | destination-port | source-dest-ip-port | source-dest-ip-port-vlan | source-dest-ip-vlan | source-dest-mac | source-dest-port | source-ip-port | source-ip-port-vlan | source-ip-vlan | source-mac | source-port} [module-number]
To Summarize: I cannot say which port would be selected, it purely depends on type of frame you are sending with the combination of the load-balance method.
After tweaking you can also know from the command which link the traffic is taking,
NEXUS2-SPAN# show port-channel load-balance forwarding-path interface port-channel 71 src-ip 1.1.1.1 dst-ip 2.2.2.2 vlan 51 module 2
Module 2: Missing params will be substituted by 0's.
Load-balance Algorithm: src-dst ip-l4port
RBH: 0xb0 Outgoing port id: Ethernet8/8
we can also try tweaking the same load-balancing on the 2960 also. It purely depends on the load-balancing algorithm. Below is for 2960 Load-balancing tweaking,
http://www.cisco.com/en/US/docs/switches/lan/catalyst2960/software/release/12.2_53_se/configuration/guide/swethchl.html
Even after doing this i wouldnt say 100% it would select one link.
Hope this helps!
Thanks,
Richard.
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Design help related to ACE to Switch connectivity using Port-Channel

Hi,
I have a Cisco ACE 4710 configured in One-Arm mode. This ACE is getting connected with 2 3750 switches. These 2 3750 switches connected in trunk mode.
ACE is connected to these 3750 switches using Port-channel.
ACE Config:
================================
interface gigabitEthernet 1/1
description One-arm mode port to DMZ Switch 1 port 20
channel-group 1
no shutdown
interface gigabitEthernet 1/2
description One-arm mode port to DMZ Switch 2 port 20
channel-group 1
no shutdown
interface port-channel 1
switchport access vlan 51
port-channel load-balance src-dst-ip
no shutdown
interface vlan 51
ip address 10.40.56.131 255.255.255.128
access-group input everyone
access-group output everyone
nat-pool 1 10.40.56.215 10.40.56.215 netmask 255.255.255.255 pat
service-policy input LB
service-policy input remote-access
no shutdown
===========================================================
The problem is that 3750 switches are not stacked.
Application is working fine. But i am getting a lot of MAC flapping messages..
kindly suggest whether this design is OK or something needs to be done to rectify it...
Attached a small diagram..

Hello acharyr123,
I don't think this design is ok, and it would cause mac flapping since the two indepedendent 3750 switches will learn the ace mac addresses off of two different interfaces. The 3750s would have to be stacked so that they would act as one switch then this should work correctly.
Thanks
Joel Lamousnery
TAC CSE

Nexus - port-channel load balancing

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