IP CEF load balancing

Hi,
I am slightly confused with the default load balancing method used by CEF (Per Destination load balancing).
I have 2 links and i would like to know how the router decides to use the links for a flow.
I have been having trouble with 2 links which are load balancing on per destination CEF. I see around 90 % utilization in the 1st pipe and only 70% on the second. Because of this the latency on the first pipe shoots up drastically causing applications to hang. AT all these times the 2nd pipe latency is always normal.
I Would like to know whether some fine tuning is required for CEF per destination to work properly.

Narayan
With per-destination load sharing (or load balancing) whether it is with CEF or the older fast switching you may likely get some difference on the individual links. This is because some destinations are likely to get more traffic and some destinations will get less traffic. While this type of load share is pretty close it will not be exact. Note that even if you do per packet load share the load may not be exactly even because there could be larger packets on one link and smaller packets on the other link (and per packet balancing does introduce the probability of out of order packets).
If you want really equal distribution of traffic over the links then you should probably consider putting both serial links into a multilink PPP configuration. MLPPP will give you even distribution of traffic on both links.
HTH
Rick

Similar Messages

If equal cost routes exist, OSPF uses CEF load balancing?

Hi All,
Can anyone explain about:
. If equal cost routes exist, OSPF uses CEF load balancing?

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Posting
Rick is correct, but if his response, with mine, causes any confusion. . .
To OP's original question:
If equal cost routes exist, OSPF uses CEF load balancing?
The answer is technically no, for the reason Rick describes.
But if we rephrase, such as:
Does CEF load balance across multiple equal cost routes generated by OSPF?
The answer would be yes.
I suspect the latter question is what the OP really had in mind, but again, Rick is correct to distinguish that OSPF doesn't use CEF.

Load-balancing in MPLS Core

How is load-balancing achieved in MPLS L3 vpns and equal cost multiple links exist to reach egress PE along with per-destination load-balancing enabled on interfaces.
I have tried to simulate the network below
Ingress PE--->P1--->>P2--->Egress PE
Multiple equal cost links exist between P1 and P2, cisco platform,LDP, IGP-ospf being used.

Hi,
Destination based load balancing in MPLS L3VPNs can be categorized into two scenarios:
1) multiple pathes between two PE routers
2) multiple access links to a single CE or site
Your question as I understand it was about the first scenario. So let me first quickly review how customer traffic is forwarded between VRFs on two different PE routers.
The VRF routing table will have BGP entries for the routes learned from the remote PE usually with next hop addresses being the remote PE loopback IP used for PE-to-PE BGP peering.
The traffic will be forwarded across P routers using the label for the BGP next hop.
Thus the load balancing accross the MPLS core in a first step is decided by the IGP, which has to insert several equal cost pathes into the global routing table for the BGP next hop networks (PE loopbacks).
Side note: MPLS traffic engineering in the core would allow for unequal cost load balancing.
The decision, which labeled packet to send across which path in the core is done by CEF using a hash algorithm. To achieve the same load balancing as with unlabeled IP traffic, a Cisco MPLS enabled router will look for the bottom label - the one with bottom-of-stack bit set to 1 - and try to determine, if the transported packet behind the bottom label is IP. If so, the hash is calculated for the customer IP header like for normal IP traffic. This ensures all traffic for a certain customer destination will always go through the same path. No unwanted packet reordering will occur.
Be aware, that the customer IP packet header will only be used for CEF hash calculation, no IP lookup will be performed, as core routers in MPLS L3VPNs do not have any knowledge about customer addresses.
As a side note: if the traffic transported is not IP (e.g. Ethernet over MPLS), the bottom label will be used for the CEF load balancing (e.g. the VC label).
For the second scenario - CE load balancing with multihomed CE/sites - it is first required to have two equal cost entries in the VRF routing tables. The difference will be the two different PE BGP next hop addresses. The first load balancing decision is the performed by CEF based on the IP packet received by the CE and the VRF routing table entries. Once CEF decided, which VRF entry to use, the required BGP next hop label (and the VPN label) is applied and the packet is transported across the MPLS core. load balancing there is done as described above.
Hope this helps! Please rate all posts.
Regards, Martin

CRS-1 Load balancing issue

Dear all,
I am using a simple load balacing based on static routing, running V 3.8.4.
Although checking route and cef details confirms load balancing is as it should be...load on interfaces is very much apart for outpout traffic (input looks fiine).
load interval and configuraion on each interface is exactely the same, no bundling used.
Any thoughts ?
TIA
Samir

Samir,
The load balancing algorithm used in CRS by default is based on L3, 3 tuple, hash. So if you don't have enough different l3 source/destination addresses you won't see as even distribution. Normally this is just fine. But depending on the traffic flows you have you may need to go to L4, 7 tuple, algorithm. This will then look deeper into the packets and use the L4 ports along with source and destinations addresses to balance out the flows.
To change this it's global config command "cef load-balancing fields l3/l4".
This will change the hashing algorithm used on the linecards for load balancing.
Thanks,
Bryan

Load Balancing 2 routers

Hi all
Can someone tell me the best way to load balance between 2 routers, can someone post a typical config ?
thanks a million
Carl

Hi Carl,
You can use the following load-blancing methods between the routers.
1. Static routes or default route load-balancing
2. Multilink PPP
3. Equal/unequal cost path load-balancing with Dynamic Routing protocol.
4. CEF load-balancing.
Please see the DOC below.
http://www.cisco.com/en/US/products/hw/modules/ps2033/products_white_paper09186a0080091d4b.shtml
I have multilink PPP and static route load-balancing config handy with me. Please see below :
interface Multilink1
ip address 193.193.193.1 255.255.255.252
ppp multilink
multilink-group 1
interface Serial0/2
no ip address
encapsulation ppp
ppp multilink
multilink-group 1
interface Serial0/3
no ip address
encapsulation ppp
ppp multilink
multilink-group 1
interface Serial1/1:0
ip address 192.168.170.1 255.255.255.0
encapsulation ppp
no ip route-cache
interface Serial1/2:0
ip address 192.168.180.1 255.255.255.0
encapsulation ppp
no ip route-cache
ip route 172.28.20.0 255.255.255.0 192.168.170.2
ip route 172.28.20.0 255.255.255.0 192.168.180.2
HTH,
-amit singh

ASA load balance per destination

Hello,
I have an ASA with version 8.4.4.1 connected via a switch to two routers and I have two default routes on the ASA pointing to the two routers.
The question is : Does the ASA load balance the traffic onto the two routers per-destination or per-packet?
As in routers, CEF load balances the connection per-destination by default. So, what about the ASA regardless of the hardware.
Regards,
George

No. Everything will go to lowest cost route. Matthew

MPLS Load Balancing/Sharing with TE or CEF or Both?

So I am just playing around in GNS3 trying to set up multiple ECMP links between to P routers like this;
CE1 -- PE1 -- P1 == P2 -- PE2 -- CE2
(There are actually four links between P1 & P2!)
I have set up a pseudoswire xconnect from PE1 to PE2 so CE1 & 2 can ping each other on the same local subnet range. That works just fine.
My question is this:
I have configured "ip load-sharing per-packet" on each of the four interfaces on P1 and P2 that are facing each other (I know per-packet balancing is frowned upon but lets not talk about that right now!) and this works, traffic is distributed across all links (I can see with packet captures in GNS3).
Where does "ip load-sharing per-packet" fit in to the chain of events with regards to MPLS and CEF etc?; So, with MPLS enabled everywhere the two P routers are forwarding based on labels and not IP address. With MPLS enabled, does this command force the P routers to load-balance each MPLS frame as it comes in, round-robbin'ing the ingress frames across all links, the same as it would if it were a plain IP packet? So the command is ignorate of the kind of traffic being used? Or is the P router looking down into the MPLS frame for the IP in the IP packet?
Also, in order to get the same sort of performance boost you get from per-packet load balancing, seeing as I am using MPLS here, should I be using some francy MPLE TE to do this instead of that interface sub-command?
If I remove that command, I seem to always use link 2 for sending traffic towards P2 from P1, and link 3 for receiving the return traffic from P2 to P1. This is presumably because the ICMP packets have nothing to hash on except the source and destination IP addresses, so they always hash to the same physical links. Without using that command how else can I make use of the four links?

Hello Jwbensley,
first of all,
"ip load-sharing per-packet" is not a viable option as it causes out of order issues.
Real world devices perform load balancing based on the second (more internal ) label value so to achieve some load balancing for example multiple pseudowires must be defined between the same pair of PE nodes.
L3 VPN use different internal labels for different customer prefixes of the same VRF site ( unless some special command is used to say use one label per VRF site)
>> f I remove that command, I seem to always use link 2 for sending traffic towards P2 from P1, and link 3 for receiving the return traffic from P2 to P1
This is the expected behaviour in this scenario.
With MPLS TE you can achieve results similar to the use of multiple pseudowires /LSPs : forms of load sharing not true load balancing. In all cases in MPLS world flow based and not per packet
Hope to help
Giuseppe

MPLS TE load-balancing --- CEF Problem

Dears
Would like your assistance please regarding below issue
We are having 5 TE tunnels going to same destination and we are doing load-balancing between these 5 LSPs TE tunnels.
Command "mls ip cef load-sharing full simple" is configured so that CEF will use L4 ports in its algorithm
Problem that due to CEF behavior, 2 link are v.highly utilized and the other 3 utilization are below average
What I am thinking of but not sure If this will help or not is to have 2 TE tunnels instead of 5
1 TE tunnel load balancing on 3 links ( This can be done by using static route to tail loopback poiting to the 3 links) and another TE tunnel load balancing on the other 2 links
By doing this, I think CEF would be used 2 times; first to determine which TE tunnel to use then to determine which link within the tunnel
Will this help ?
For example
interface Tunnel1
ip unnumbered Loopback0
mpls ip
tunnel destination 10.0.0.1
tunnel mode mpls traffic-eng
tunnel mpls traffic-eng autoroute announce
tunnel mpls traffic-eng path-option 1 dynamic
tunnel mpls traffic-eng fast-reroute
ip route 10.0.0.1 255.255.255.255 link-1
ip route 10.0.0.1 255.255.255.255 link-2
ip route 10.0.0.1 255.255.255.255 link-3

Hello Sherif,
traffic of a single TE tunnel will not be load balanced over multiple physical links as the TE tunnel is setup using a reservation and the path will use only one link for each router hop.
So moving to two TE tunnels is not an option for you.
Hope to help
Giuseppe

CEF and per-packet load balancing

We have four OC3 links across the atlantic and I was looking for a solution which would allow load balacing across the four links on a per-packet basis (not session). The objective is both resiliency i.e. being able to handle link failures transparently & balancing the load across all the links. BGP multptah looked like the ideal soultion. However, I was told that the CEF packet based load balancing is no longer supported by CISCO. Is this correct ? Is it applicable for all models ? Are there any other potential solutions?
Appreciate a response from the experts.

Hello Rittick,
an MPLS pseudowire will use only one link of the 4 links based on inner MPLS label, it cannot be spread over multiple parallel links.
The MPLS pseudowire can travel within an MPLS TE LSP that can be protected by FRR.
per packet load balancing does not apply to your scenario.
You need to mark traffic of the critical application with an appropriate EXP settings. The EXP bits are copied to the outer (external) label.
On the OC-3 physical interfaces you will configure a CBWFQ scheduler providing 100 Mbps of bandwidth to traffic with specific EXP marking. This is elastic and over unused links bandwidth will be left available to other traffic.
On the LAN interface you need to mark the EXP bits in received packets using a policy-map
access-list 101 permit tcp host x.x.x.x host y,y,y,y
class CLASSIFY-BACKUP
match access-group 101
policy-map MARKER
class CLASSIFY-BACKUP
set mpls exp 3
class class-default
set mpls exp 0
int gex/y/z
service-policy in MARKER
class-map BACKUP
match mpls exp 3
policy-map SCHED-OC3
class BACKUP
bandwidth 100000
class class-default
fair-queue
int posx/y/z
service-policy out SCHED-OC3
applied on all pos interfaces. The MPLS pseudowire will use one link only. Different pseudowires can use different OC-3 links. Load balancing of MPLS traffic is based on internal label (the VC label of the pseudowire)
Note:
you should check if it is possible to mark traffic received on the incoming interface of the pseudowire otherwise you need to mark IP precedence nearer to the host.
Hope to help
Giuseppe

How does CEF perform equal and unequal cost load balancing?

hello
How does CEF perform equal and unequal cost load balancing?
thanks

Hello Wang,
it is only EIGRP that can perform load balancing over unequal cost links.
For equal cost links CEF allocates 16 buckets and maps them to the the physical links.
the result of a binary operation is used to associated a packet to an outgoing interface:
Source IP address EXOR DEstination IP Address EXOR hash
the hash is a seed that changes only at every reload.
Actually the last 4 bits are used so that each flow can be classified in one bucket.
then the outgoing interface is the one asscociated to the result of the exor operation.
Another way to see is that m bits are used so that 2^m is equal to N number of links (if N is even)
the rule is simple and pre-established
Hope to help
Giuseppe

MPLS TE equal or unequal load balancing doesn't work? - step2

Previous question in thread:
Dear Sir!
I've two MPLS TE tunnels from one PE to another PE.
And there are traffic share count between them
(as tunnel mpls traffic-eng load-share command define).
But in real life all traffic from the same source to the same destination go through only one tunnel
(as CEF define - i.e. how sh ip cef exact-route says).
PEs are 3660 platforms with c3660-jk9o3s-mz.123-8.T
installed.
How can I correct this problem?
But this answer does not solved my issue:
hritter - Network Consulting Engineer, CISCO SYSTEMS, CCIE
Aug 4, 2004, 7:20am PST
This is expected behavior since CEF is used at the head end to perform label imposition. I wouldn't recommend changing the default bahavior to per=packet loadsharing since this could lead to of of sequence packets, which could lower the overall performance.
Hope this helps,
so my secound question:
Dear Sir!
I'm agree with you as MPLS TE tunnels are opened from PE to PE, so CEF does it work.
But if I open this tunnels from P to PE, ONLY ONE of this tunnels are used instead of load-sharing, if traffic go from one source (of site1 of VPN1) to the same destination (located at site2 of VPN1).
Why? Packet through P-devices swithes by labels, so I mean that CEF cannot does src-dst load sharing?
My problem are that I must to do load sharing between this two tunnels in the case above.
Q: How can I solve this problem?
Best regards,
Maxim Denisov

The per session load-balancing is also used by MPLS when multiple paths are available. Changing this behavior to per-packet is still not recommended.
Hope this helps,

Disable load balancing on dual PRIs - 3640 with MICA modems for dial out

We have a custom application that connects through reverse telnet to a Cisco 3640 that has 2 NM-24DM modules and 2 PRIs connected to it. Currently all outgoing calls are getting load balanced over the two PRIs. I need to change that so that all calls go over the first PRI and when all channels are used up, it starts using the second PRI. Seems like a simple enough thing to do but I can't figure out how to.
Here is my config
Current configuration : 1401 bytes
version 12.4
service timestamps debug uptime
service timestamps log uptime
service password-encryption
hostname DIALOUT01
boot-start-marker
boot-end-marker
enable secret 5 xxxxxxx
no aaa new-model
clock timezone EST -5
clock summer-time EDT recurring
no ip routing
no ip cef
no ip domain lookup
ip domain name xxxxxxx.xxx
isdn switch-type primary-ni
controller T1 0/0
framing esf
linecode b8zs
pri-group timeslots 1-24
description xxxx
controller T1 0/1
framing esf
linecode b8zs
pri-group timeslots 1-24
description xxxx
interface FastEthernet0/0
ip address dhcp hostname dialout01
no ip route-cache
no ip mroute-cache
duplex auto
speed auto
interface Serial0/0:23
no ip address
encapsulation hdlc
isdn switch-type primary-ni
no fair-queue
no cdp enable
interface Serial0/1:23
no ip address
encapsulation hdlc
isdn switch-type primary-ni
no fair-queue
no cdp enable
no ip http server
control-plane
line con 0
line 33 56
modem InOut
modem autoconfigure type mica
transport preferred telnet
transport input telnet
transport output telnet
line 65 88
modem InOut
modem autoconfigure type mica
transport preferred telnet
transport input telnet
transport output telnet
line aux 0
line vty 0 4
password 7 xxxxx login
end
Thanks,
Shahid

If I understand the question I think that isdn bchan-number-order is the command you are interested in. I think it detaults to round-robin, sounds like you want ascending (that is isdn bchan-number-order ascending). It is an interface subcommand.
See http://www.cisco.com/en/US/docs/ios/12_3t/12_3t2/feature/guide/gt_ibcac.html#wp1055853
That may only apply to native ISDN calls and not MICA based calls, but see if that helps.

Load balancing weirdness using NAT and same-metric route

Hi.
I'm trying to set up a double-WAN load-balancing scenario:
I decided to attempt the "multiple same-metric routes with NAT" approach so I went for the example used in the IOS NAT Load-Balancing for Two ISP Connections Configuration Guide [1].
I decided to use an upside-down Cisco 871-SEC/K9: use Vlan1 and Vlan2 for the routers and Fa4 for the LAN. I am hoping this is not an issue.
There is this weirdness with some connections, particularly FTP. I pinpointed the problem to the following scenario: if I do a couple of pings to 100.1.1.1 using the FastEthernet4 as the source address, this is what I get in the logs:
=== PING 1 ECHO REQUEST ===
*Mar 3 04:38:43.521: IP: tableid=0, s=192.168.60.4 (FastEthernet4), d=100.1.1.1 (Vlan1), routed via RIB
*Mar 3 04:38:43.521: NAT: s=192.168.60.4->10.129.124.2, d=100.1.1.1 [14152]
*Mar 3 04:38:43.521: IP: s=10.129.124.2 (FastEthernet4), d=100.1.1.1 (Vlan1), g=10.129.124.1, len 60, forward
*Mar 3 04:38:43.521: ICMP type=8, code=0
=== PING 1 ECHO REPLY ===
*Mar 3 04:38:45.589: NAT*: s=100.1.1.1, d=10.129.124.2->192.168.60.4 [19824]
*Mar 3 04:38:45.589: IP: tableid=0, s=100.1.1.1 (Vlan1), d=192.168.60.4 (FastEthernet4), routed via RIB
*Mar 3 04:38:45.589: IP: s=100.1.1.1 (Vlan1), d=192.168.60.4 (FastEthernet4), g=192.168.60.4, len 60, forward
*Mar 3 04:38:45.589: ICMP type=0, code=0
=== (something else) ===
*Mar 3 04:38:52.353: RT: SET_LAST_RDB for 0.0.0.0/0
OLD rdb: via 10.129.124.33, Vlan2
NEW rdb: via 10.129.124.1, Vlan1
=== PING 2 ECHO REQUEST ===
*Mar 3 04:38:52.353: IP: tableid=0, s=192.168.60.4 (FastEthernet4), d=100.1.1.1 (Vlan2), routed via RIB
*Mar 3 04:38:52.353: NAT: s=192.168.60.4->10.129.124.2, d=100.1.1.1 [14159]
*Mar 3 04:38:52.353: IP: s=10.129.124.2 (FastEthernet4), d=100.1.1.1 (Vlan2), g=10.129.124.33, len 60, forward
*Mar 3 04:38:52.353: ICMP type=8, code=0
=== PING 2 ECHO REPLY ===
*Mar 3 04:38:53.029: NAT*: s=100.1.1.1, d=10.129.124.2->192.168.60.4 [19825]
*Mar 3 04:38:53.029: IP: tableid=0, s=100.1.1.1 (Vlan1), d=192.168.60.4 (FastEthernet4), routed via RIB
*Mar 3 04:38:53.033: IP: s=100.1.1.1 (Vlan1), d=192.168.60.4 (FastEthernet4), g=192.168.60.4, len 60, forward
*Mar 3 04:38:53.033: ICMP type=0, code=0
In the section "Ping 2 Echo Request" line 2 shows the NAT translating the packet to the address for the first provider but line 3 shows it routing it through the second one.
In this case, the ICMP packet goes through but it is problematic if the ISP restricts the service by source-address (like RPF) or there is some acceleration mechanism inside the provider cloud, other than just plain routing.
What am I missing? Here is the relevant part of the configuration. I deliberately disabled CEF to be able to debug the messages, but I *think* this may be altering the actual router behavior. This router does not have a "debug ip cef packet" command.
no ip cef
ip dhcp pool lan-side
import all
network 192.168.60.0 255.255.255.0
default-router 192.168.60.1
domain-name doublewan.local
dns-server 8.8.8.8 8.8.4.4
lease infinite
ip domain name doublewan
interface FastEthernet0
!doesn't appear on running-config: vlan 1 is the default access vlan
!switchport access vlan 1
interface FastEthernet1
switchport access vlan 2
interface FastEthernet2
shutdown
interface FastEthernet3
shutdown
interface FastEthernet4
ip address 192.168.60.1 255.255.255.0
ip nat inside
ip virtual-reassembly
no ip route-cache
duplex auto
speed auto
interface Vlan1
ip address 10.129.124.2 255.255.255.224
ip nat outside
ip virtual-reassembly
no ip route-cache
interface Vlan2
ip address 10.129.124.35 255.255.255.224
ip nat outside
ip virtual-reassembly
no ip route-cache
ip route 0.0.0.0 0.0.0.0 Vlan1 10.129.124.1
ip route 0.0.0.0 0.0.0.0 Vlan2 10.129.124.33
ip nat inside source route-map nat1 interface Vlan1 overload
ip nat inside source route-map nat2 interface Vlan2 overload
ip access-list standard acl4-nexthop-vlan1
permit 10.129.124.1
ip access-list standard acl4-nexthop-vlan2
permit 10.129.124.33
route-map nat2 permit 10
match ip address 102
match ip next-hop acl4-nexthop-vlan2
match interface Vlan2
route-map nat1 permit 10
match ip address 101
match ip next-hop acl4-nexthop-vlan1
match interface Vlan1
control-plane
Of course, there is some configuration pending for redundancy and stuff.
Thanks a lot in advance.
[1] http://www.cisco.com/c/en/us/support/docs/ip/network-address-translation-nat/100658-ios-nat-load-balancing-2isp.html

Hello.
This might be a bug in debug command or the IOS (without ip cef) you use; as routing is done before NAT (inside to outside).
To make sure it works fine with ip cef, just enable strict uRPF (or just ACL) on .1 and .33 interfaces and see if you see any packet sent over wrong interface.
PS: please check "sh ip cef 100.1.1.1"; I guess ip cef would tell you "per-destination sharing".

Load Balancing on DSL link

Dear All,
We are having 2 internet link from 2 separate ISP.
Please help me in doing load balancing on this 2 ADSL LINK.
Thanks/Regards
Atul

Hello,
here is a sample configuration for load balancing with 2 links:
ip cef
interface FastEthernet0/1
ip address 192.168.1.1 255.255.255.0
ip nat inside
interface ATM0
no ip address
no ip route-cache
no atm ilmi-keepalive
dsl operating-mode auto
interface ATM0.1 point-to-point
no ip route-cache
pvc 0/38
encapsulation aal5mux ppp dialer
dialer pool-member 1
interface ATM0.2 point-to-point
no ip route-cache
pvc 0/38
encapsulation aal5mux ppp dialer
dialer pool-member 2
interface Dialer1
description ISP1_Connection_1
ip address dhcp
ip mtu 1452
encapsulation ppp
dialer pool 1
dialer-group 1
ppp authentication chap pap callin
ppp chap hostname USERNAME
ppp chap password 0 PASSWORD
ppp pap sent-username USERNAME password PASSWORD
interface Dialer2
description ISP1_Connection_2
ip address dhcp
ip mtu 1452
encapsulation ppp
dialer pool 2
dialer-group 1
ppp authentication chap pap callin
ppp chap hostname USERNAME
ppp chap password 0 PASSWORD
ppp pap sent-username USERNAME password PASSWORD
ip nat inside source route-map ISP1_Connection_1 interface Dialer1 overload
ip nat inside source route-map ISP1_Connection_2 interface Dialer2 overload
access-list 1 permit 192.168.1.0
route-map ISP1_Connection_1 permit 10
match ip address 1
match interface Dialer1
route-map ISP1_Connection_2 permit 10
match ip address 1
match interface Dialer2
ip route 0.0.0.0 0.0.0.0 Dialer1
ip route 0.0.0.0 0.0.0.0 Dialer2
dialer-list 1 protocol ip permit
Regards,
GP

Load Balancing with OSPF and maximum-paths command

Hello,
Just a quick query really, we have a disribution layer 3 switch, in its routing table it has 3 default routes all with the same metric from the core router, this is because the core router is setup with the comamnd "default-information originate always metric 50" which obviously proagates the default route around the area and the metric never changes from 50.
So i have a routing table that looks like this:
O*E2 0.0.0.0/0 [110/50] via 77.95.176.9, 06:44:51, GigabitEthernet4/9
[110/50] via 77.95.176.17, 06:44:51, Vlan903
[110/50] via 91.203.72.5, 06:44:51, Vlan262
Three default routes with the same metric, does this mean that the router IOS will load balance traffic over all three routes evenly? I mean i have been reading up on it and appartemtly i dont have the command "maximum-paths 3" under my ospf process?
I have been doing some traceroutes from this switch to the internet (various sites) and all the traffic seems to be going out over the first route in the table that next hop is 77.95.176.9
My question is how can i verify that load balancing is taking place, or if its not then i need to add this "maximum-paths 3" command to the ospf on the local switch? I would say load balancing is not taking place but im sure i have seen traffic from one customer being routes over all 3 paths due to matching spikes on the SNMP sensors?
Many Thanks.
Matt

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Yes, your traffic should use all three paths, as Rick notes, OSPF, on Cisco, normally defaults to using up to 4 equal cost paths.
As Rick also notes mentioning CEF, how actual traffic is forwarded across ECMP can vary. Often, the device will keep all traffic for the same flow on the same egress port, and attributes selected for actual egress port selection might be deterministic. I.e. it's possible same traffic flow will always be sent to the same egress port. (This means even with ECMP, you may not see an equal load distribution.)

IP CEF load balancing

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