Nebula Switch - RSTP or Loop Guard ?

GiuseppeR

Hello everyone,

I see that on Nebula is impossible to have RSTP and Loop Guard active at the same time, if you try to have both you get this error:

"You cannot enable loop guard and spanning tree on a port at the same time"

I tried to have both active because I saw this link:

https://community.zyxel.com/en/discussion/20934/the-choice-between-loopguard-and-spanning-tree

Here you read that "Loop guard is a feature that provides an additional layer of protection" while in reality it has to be an alternative to RSTP becuase you cannot have both at the same time.

I know that RSTP prevents network loops by blocking redundant ports, but I'm looking for some real scenarios.

What would you choose and why?

I'm curious about your environments.

Zyxel_Kay

Hi @GiuseppeR

Yes, the Loop Guard and RSTP cannot be enabled simultaneously on a switch port.

As mentioned in the FAQ article, RSTP is used to prevent broadcast storms created by ring topologies. Loop Guard, on the other hand, is particularly useful for ports connecting to end devices or hubs. For example, if your switch connection is in a ring topology, you should apply RSTP on those ports. For ports connecting to end devices or hubs, you can set up Loop Guard to prevent loops.

Let me know if you have any other questions.

Thanks.

Zyxel_Kay

Hi @GiuseppeR

Usually, RSTP is used to interconnect RSTP-compliant switches.

RSTP-aware switches periodically exchange Bridge Protocol Data Units (BPDUs). When the LAN topology changes, a new spanning tree is constructed. Once a stable network topology is established, all bridges listen for Hello BPDUs from the root bridge. If a bridge does not receive a Hello BPDU after a predefined interval (Max Age), it assumes the link to the root bridge is down. The bridge then initiates negotiations with other bridges to reconfigure the network and re-establish a valid topology.

For ports connecting to end devices, using Loop Guard is beneficial because it adds an extra layer of protection against loops. Using RSTP on these ports generally does not provide additional benefits since end devices do not participate in the spanning tree process.

Zyxel_Kay

Hi @GiuseppeR

Yes, the Loop Guard and RSTP cannot be enabled simultaneously on a switch port.

As mentioned in the FAQ article, RSTP is used to prevent broadcast storms created by ring topologies. Loop Guard, on the other hand, is particularly useful for ports connecting to end devices or hubs. For example, if your switch connection is in a ring topology, you should apply RSTP on those ports. For ports connecting to end devices or hubs, you can set up Loop Guard to prevent loops.

Let me know if you have any other questions.

Thanks.

GiuseppeR

Hello @Zyxel_Kay

if I understand your post correctly you suggest me to use RSTP only on specific ports linking one switch to another one while on the other ports (especially the ones easily reachable for users….) use the Loop Guard. Is that correct?

Is there any possible benefit to have RSTP on ports to end devices?

See you soon

Zyxel_Kay

Hi @GiuseppeR

Usually, RSTP is used to interconnect RSTP-compliant switches.

RSTP-aware switches periodically exchange Bridge Protocol Data Units (BPDUs). When the LAN topology changes, a new spanning tree is constructed. Once a stable network topology is established, all bridges listen for Hello BPDUs from the root bridge. If a bridge does not receive a Hello BPDU after a predefined interval (Max Age), it assumes the link to the root bridge is down. The bridge then initiates negotiations with other bridges to reconfigure the network and re-establish a valid topology.

For ports connecting to end devices, using Loop Guard is beneficial because it adds an extra layer of protection against loops. Using RSTP on these ports generally does not provide additional benefits since end devices do not participate in the spanning tree process.