The Dynamic MAC Learning versus EVPN blog post triggered tons of interesting responses describing edge cases and vendor bugs implementation details, including an age-old case of silent hosts described by Nitzan:
Few years ago in EVPN network, I saw drops on the multicast queue (ingress replication goes to that queue). After analyzing it we found that the root cause is vMotion (the hosts in that VLAN are silent) which starts at a very high rate before the source leaf learns the destination MAC.
It turns out that the behavior they experienced was caused by a particularly slow EVPN implementation, so it’s not exactly the case of silent hosts, but let’s dig deeper into what could happen when you do have silent hosts attached to an EVPN fabric.
One of my subscribers found an unusual BGP specimen in the wild:
So far so good, and kudos to whoever realized BGP is the only sane protocol to run between virtual machines and network core. However, the routing in the network core was implemented with EBGP sessions between the three core devices, and my subscriber thought the correct way to do it would be to use IBGP and OSPF.
One of my subscribers found an unusual BGP specimen in the wild:
So far so good, and kudos to whoever realized BGP is the only sane protocol to run between virtual machines and network core. However, the routing in the network core was implemented with EBGP sessions between the three core devices, and my subscriber thought the correct way to do it would be to use IBGP and OSPF.
netlab release 1.5.2 brings another bunch of cool features, including:
I’ll cover these features in separate blog posts; today I wanted to highlight a few minor additions:
netlab release 1.5.2 brings another bunch of cool features, including:
I’ll cover these features in separate blog posts; today I wanted to highlight a few minor additions:
BGP zombies are routes in the BGP table that refuse to disappear even though they should have been long gone. Recent measurements estimate between 0.5% and 1.5% of all routes in the global BGP table are zombies, which sounds crazy – after all, BGP is supposed to be pretty reliable.
Daryll Swer identified one potential source – Juniper routers do not revoke suppressed aggregated prefixes – and documented it in Navigating a BGP zombie outbreak on Juniper routers.
BGP zombies are routes in the BGP table that refuse to disappear even though they should have been long gone. Recent measurements estimate between 0.5% and 1.5% of all routes in the global BGP table are zombies, which sounds crazy – after all, BGP is supposed to be pretty reliable.
Daryll Swer identified one potential source – Juniper routers do not revoke suppressed aggregated prefixes – and documented it in Navigating a BGP zombie outbreak on Juniper routers.
Want to know some details behind the CloudFlare SD-WAN implementation? You might find them in From IP packets to HTTP: the many faces of our Oxy framework.
I don’t know enough about Linux networking to figure out whether one could use those details to build something similar, but CloudFlare blog posts keep begin much better than Google’s Look How Awesome We Are recruitment drives.
Want to know some details behind the CloudFlare SD-WAN implementation? You might find them in From IP packets to HTTP: the many faces of our Oxy framework.
I don’t know enough about Linux networking to figure out whether one could use those details to build something similar, but CloudFlare blog posts keep begin much better than Google’s Look How Awesome We Are recruitment drives.
Lukas Krattiger wrapped up his EVPN-versus-MLAG presentation (part of EVPN Deep Dive webinar) with an overview of the advantages and drawbacks of EVPN-based multihoming solutions:
Lukas Krattiger wrapped up his EVPN-versus-MLAG presentation (part of EVPN Deep Dive webinar) with an overview of the advantages and drawbacks of EVPN-based multihoming solutions:
I got this question from one of my readers:
Why are OSPF and BGP are more complex than STP from a designer or administrator point of view? I tried everything to come to a conclusion but I couldn’t find a concluded answer, ChatGPT gave a circular loop answer.
There are numerous reasons why a protocol, a technology or a solution might be more complex than another seemingly similar one (or as Russ White would have said, “if you haven’t found the tradeoffs, you haven’t looked hard enough"):
I got this question from one of my readers:
Why are OSPF and BGP are more complex than STP from a designer or administrator point of view? I tried everything to come to a conclusion but I couldn’t find a concluded answer, ChatGPT gave a circular loop answer.
There are numerous reasons why a protocol, a technology or a solution might be more complex than another seemingly similar one (or as Russ White would have said, “if you haven’t found the tradeoffs, you haven’t looked hard enough”):
One of my readers worried about the control-plane-induced MAC learning lag in EVPN-based networks:
In all discussions about the advantages/disadvantages of VXLAN/EVPN, I can’t find any regarding the lag in learning new macs when you use the control plane for mac learning.
EVPN is definitely slower than data plane-based dynamic MAC learning (regardless of whether it’s done in hardware or software), but so is MLAG.
One of my readers worried about the control-plane-induced MAC learning lag in EVPN-based networks:
In all discussions about the advantages/disadvantages of VXLAN/EVPN, I can’t find any regarding the lag in learning new macs when you use the control plane for mac learning.
EVPN is definitely slower than data plane-based dynamic MAC learning (regardless of whether it’s done in hardware or software), but so is MLAG.
You can configure many firewalls to act as a router (layer-3 firewall) or as a switch bridge (layer-2 firewall). The oft-ignored detail: how does a layer-2 firewall handle ARP (or any layer-2 protocol)?
Unless you want to use static ARP tables it’s pretty obvious that a layer-2 firewall MUST propagate ARP. It would be ideal if the firewall would also enforce layer-2 security (ARP/DHCP inspection and IPv6 RA guard), but it looks like at least PAN-OS version 11.0 disagrees with that sentiment.
Straight from Layer 2 and Layer 3 Packets over a Virtual Wire:
You can configure many firewalls to act as a router (layer-3 firewall) or as a switch bridge (layer-2 firewall). The oft-ignored detail: how does a layer-2 firewall handle ARP (or any layer-2 protocol)?
Unless you want to use static ARP tables it’s pretty obvious that a layer-2 firewall MUST propagate ARP. It would be ideal if the firewall would also enforce layer-2 security (ARP/DHCP inspection and IPv6 RA guard), but it looks like at least PAN-OS version 11.0 disagrees with that sentiment.
Straight from Layer 2 and Layer 3 Packets over a Virtual Wire:
Anne Baretta decided to use netlab to test a proposed DMVPN topology. As netlab doesn’t support DMVPN (and probably never will), he decided to use netlab capabilities to start the lab topology and perform initial configuration, adding DMVPN configuration commands as custom configurations. Here’s how he described the process:
In this case I used netlab as a quick way to get a topology up and running, and then add the DMVPN configuration by hand.
Anne Baretta decided to use netlab to test a proposed DMVPN topology. As netlab doesn’t support DMVPN (and probably never will), he decided to use netlab capabilities to start the lab topology and perform initial configuration, adding DMVPN configuration commands as custom configurations. Here’s how he described the process:
In this case I used netlab as a quick way to get a topology up and running, and then add the DMVPN configuration by hand.
Avery Pennarun published a lovely rambling on magic, science, engineering and a pinch of AI. You might enjoy reading it1 with your Sunday morning coffee 😎.