Why not every layers of routers and switches also do load balancing?

[Maivoko]

Why not every layers of routers and switches also do load balancing?

Do people have experience load balancing at BGP+OSPF router , load balancing at first layer firewall , load balancing at switches between layers of firewalls, load balancing at second layer firewall , , load balancing at third layer firewall , load balancing at core switch router at the same time ? 

it is like full path load balancing.

Is it really asymmetric routing happened when load balancing all layers ?

[M02@rt37]

Hello @Maivoko 

Load balancing is typically implemented where traffic is expected to be high and requires traffic to be spread across multiple paths. Load balancing may not be necessary or practical for all layers of the network, depending on the network's design and traffic patterns.

Load balancing at multiple layers of the network can be beneficial, but it can also result in asymmetric routing, which can cause issues with some network applications. Asymmetric routing occurs when traffic to and from a network device does not follow the same path. While this is not necessarily a problem for all network applications, it can cause issues with some applications that require symmetric routing.

To mitigate this issue, we typically design load balancing techniques that ensure symmetric routing. For example, some load balancing algorithms can ensure that traffic from a source to a destination always follows the same path, regardless of the layer of the network. This can help avoid issues with asymmetric routing and ensure optimal network performance.

[MHM Cisco World]

I could not get your Q here, can you more elaborate ?

[Joseph W. Doherty]

"Why not every layers of routers and switches also do load balancing?"

What exactly are the layers of routers and switches you're asking about and further how do you define "load balancing"?

"Is it really asymmetric routing happened when load balancing all layers ?"

How do you define "asymmetric routing"?

[Maivoko]

Asymmetric routing is outbound and inbound takes different path

layers means horizontal view of network diagram for the level it pass

I know OSPF can use ip load sharing by destination

1.If different brand of firewall use by destination, do it mean that OSPF and different brand of firewall use the same destination?

2.Does it mean switches between firewall had better not used src-dst-mac ?

[Joseph W. Doherty]

@Maivoko I've looked at your certs, multiple Cisco professional level.  Looking at this posting, and some of your other recent postings, seems you have less network knowledge that someone would expect from even a Cisco associate level.

So, also considering what you've posted, would I be correct in assuming you are NOT a native English language speaker?

If you are not a native English language speaker, nothing wrong with that!!!  However, I suspect we've might be having translation issues, i.e. it is sometimes unclear what your question really is, and conversely, my answers may be unclear too.

So, I will try to answer your questions, as clearly as possible, but if what I write is unclear, please let me know.

"Asymmetric routing is outbound and inbound takes different path"

Agreed.

"layers means horizontal view of network diagram for the level it pass"

Layers like the OSI model, correct?

"I know OSPF can use ip load sharing by destination"

Agreed.

"1.If different brand of firewall use by destination, do it mean that OSPF and different brand of firewall use the same destination?"

Is FW also running OSPF?  If it is, part of same OSPF topology as adjacent OSPF devices?

If FW running OSPF, it too should support ECMP, but what defaults for how many ECMP paths it supports, might vary from Cisco OSPF and/or its OSPF auto costing (NB: not part of OSPF RFC), if any, might be using a different basis.

"2.Does it mean switches between firewall had better not used src-dst-mac ?"

Would depend on FW implementation.  If we're discussing OSPF ECMP, it just considers equal OSPF path cost.   Src-dst-mac, would expect to only be used for L2 LB, like Cisco's Etherchannel.  (NB: Cisco's Etherchannel options vary by platform, most "modern" Cisco would offer src-dst-mac [although IMO src-dst-IP, if offered, possible better choice], but I recall decades ago LB options might only be  dst-mac and  src-mac.)