8 votes
Accepted

spanning-tree port type edge trunk on port-channel vs physical interface

Strongly suggested: Configure both port-channel and its members identically (except of course for description and the channel-group and vpc bits). As long as an interface is not configured to be ...
Marc 'netztier' Luethi's user avatar
8 votes
Accepted

How does link aggregation work in reality?

What really happens is that any one flow only uses one of the links. Different flows are assigned to different links based on a hashing algorithm, so, in aggregate, you get the full bandwidth of the ...
Ron Maupin's user avatar
  • 99.4k
7 votes

LACPDU packets to pass through unmanaged switch

As Ron Trunk pointed out, LACP uses a special multicast OUI on its frames. Your unmanaged switch does not recognize the OUI, only that it is multicast, and it sends the multicast frames to every other ...
Ron Maupin's user avatar
  • 99.4k
6 votes
Accepted

Port channel to two different switches

I understand that this is an incorrect configuration, but what was blocking traffic to the new switch? Is this part of the port channel or spanning tree or something else? Nothing was actually "...
YLearn's user avatar
  • 27.3k
6 votes

Are all router ports both input and output or are ports divided in those two categories?

Unless it's something really special, yes, all network ports on any network device are bidirectional. After all, most communications requires sending messages both ways, even if the traffic in one ...
ilkkachu's user avatar
  • 407
5 votes

How does link aggregation work in reality?

Adding to Ron's excellent answer, with the vast majority of switches there are three different hashing algorithms: MAC address (L2), IP address (L3) and IP address plus port numbers (L4). The ...
Zac67's user avatar
  • 83.9k
5 votes

Would multiple connections to a network make the connection faster?

In most instances for hosts, no. Each interface is generally a separate network. Some hosts (usually servers) can use multiple (generally a maximum of eight) connections bonded together as a single ...
Ron Maupin's user avatar
  • 99.4k
5 votes

LACPDU packets to pass through unmanaged switch

How do I route the lacpdu packets through the unmanaged switch and make the etherchannel work? Etherchannel, LACP or a static LAG trunk can't work across an unmanaged switch ever. As both Rons have ...
Zac67's user avatar
  • 83.9k
5 votes
Accepted

BGP running on VLAN interface or loopback0?

It is always recommended in BGP best practices to peer with loopback addresses for iBGP peers as we no longer have to rely on a single physical interface (or in your case a VLAN SVI) to be up/up. As ...
ditrapanij's user avatar
  • 1,307
5 votes

Are all router ports both input and output or are ports divided in those two categories?

Router ports, also called interfaces, are (almost) always 2-way.
Ron Trunk's user avatar
  • 67.3k
4 votes

vpc/mlag block half of uplink?

The whole point of MLAG / VPC is to have both link active, as in a standard link aggregation. Otherwise there would be little benefit over xSTP (spanning tree) (yes it converges faster but it's much ...
JFL's user avatar
  • 19.6k
4 votes
Accepted

Difference between port-channel lacp fallback individual VS. static?

From this ARISTA manual, page 620: Static fallback: the port channel maintains one active port while in fallback mode; all its other memberports are in standby mode until a LACP PDU is received by ...
JFL's user avatar
  • 19.6k
4 votes
Accepted

Cisco nexus vpc spanning-tree port type trunk question

SW3 is a switch. By first principle, portfast [trunk] or port type edge [trunk] should not be enabled on ports that connect to switches, lest you risk loops if that other switch connects to some other ...
Marc 'netztier' Luethi's user avatar
4 votes

LACPDU packets to pass through unmanaged switch

You probably can't with a single switch. LACP frames are multicast, so the unmanaged switch will flood them out all ports. This will cause several problems: The sending switch will see its frame ...
Ron Trunk's user avatar
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4 votes
Accepted

Help optimize a LAG with LACP and two different algorithms on each side

We don't have router, all we have L2 switch network. We have many servers behind trunk, so should i use src-dsp-ip? or src-dst-mac ? You need to weigh several factors to determine which method to ...
Ron Maupin's user avatar
  • 99.4k
4 votes
Accepted

Port cost relation to data rate capacity

For routing protocols, “cost” might be better called “preference.” Presumably you would prefer higher bandwidth links, so they have lower cost.
Ron Trunk's user avatar
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4 votes

Are all router ports both input and output or are ports divided in those two categories?

In general interfaces can be divided into three categories. A simplex interface can only transmit data in one direction. A half-duplex interface can transmit data in both directions but not at the ...
Peter Green's user avatar
  • 13.3k
3 votes
Accepted

Does link aggregation uses the full bandwidth?

That depends. If it is done correctly, each flow would get a maximum of 1 Gbps, but with multiple flows, you will be able to use the full 2 Gbps. Some people, on some equipment, can, and will, ...
Ron Maupin's user avatar
  • 99.4k
3 votes

Is it possible to make a truly active\active L3 VRRP\HSRP configuration between two Nexus in a vPC

You actually don't have to do anything. VPC paired Nexus work exactly as you want them to. The prerequisite is that all systems involved (i.e. the servers) are attached to the Nexus over a VPC ...
Marc 'netztier' Luethi's user avatar
3 votes

Port cost relation to data rate capacity

In routing, cost is a measure for how much effort it takes to process and forward a packet or stream over a link or a path. As Ron has pointed out, this pretty much corresponds to the time the data ...
Zac67's user avatar
  • 83.9k
2 votes

Is it possible to limit the number of active links in a channel group?

That's not possible with PAgP. Traffic is always aggregated across the whole LAG trunk. Splitting the trunk in two groups of two ports plus spanning tree would work (switching over to the spare trunk ...
Zac67's user avatar
  • 83.9k
2 votes
Accepted

Add links to a port channel group without downtime

Short answer: no. While the STP handover in step 4 or step 3 is usually faster than 1 second there's always a gap. Make sure you're using RSTP, MSTP or RPVST though. The original and largely obsolete ...
Zac67's user avatar
  • 83.9k
2 votes
Accepted

ASA5555-X vlans through port channel not working

I got this to work. All I had to do was restart the ASA after which it got the ip from isp dhcp... Then I had to fix the port channel config on the untagged lan part after figuring out that I need to ...
The amateur programmer's user avatar
1 vote
Accepted

Two switches, one uplink - best way to link them?

You have a problem on Switch 1. Your default route is to an address that the switch doesn't know how to reach. The default route should be ip route 0.0.0.0/0 10.3.104.3. Switch 2 knows how to reach ...
Ron Maupin's user avatar
  • 99.4k
1 vote
Accepted

How TCP find the correct application?

In TCP layer, it reads the port number from the packet, and find the application bind to this port number. TCP really doesn't look at the packets, and the packets do not contain port numbers. The ...
Ron Maupin's user avatar
  • 99.4k
1 vote

Should portfast be configured on the physical interfaces or on the logical port-channel, or both?

Port-channeling is a way to bypass the topology limitation of spanning-tree allowed to only having a single path. In spanning tree, the logical topology of the data-plane will arrange itself into a ...
Eric Fetty's user avatar
1 vote

Port Channel Hybrid Port Issue

Port channel or EtherChannel is a Cisco proprietary protocol for link aggregation (LAG). Other vendors' hardware may or may not be compatible with it. It's quite possible that it's supported on the ...
Zac67's user avatar
  • 83.9k

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