Choosing a Route: Order of Operations
In Cisco IOS packets are forwarded through the router (or Layer 3 switch) by Cisco Express Forwarding (CEF). A data structure called the CEF table contains a list of known IP prefixes and the outgoing interface that packets should be put on in order to get them onwards to their destination. That’s well and good. But how do the IP prefixes make it into the CEF table? To answer that question you have to work backwards and understand the order of operations that IOS goes through in order for a prefix to make it into the CEF table.
The answer to the question of what makes it into the CEF table confused me a bit, particularly when working with complex redistribution schemes. I would end up concentrating so much on admin distance (AD) that I would overlook the other, more important elements that went into determining what went into the CEF table. In order to improve my understanding I came up with this order of operations which helps me not only with redistribution, but in pretty much any situation where I’m trying to do traffic engineering.
You will not find this order of operations on cisco.com or in any Continue reading
Presentation: Automating Network Security
The fantastic Troopers 15 conference is in full swing… and I’m done with the presentations ;) The last talk I had during the conference focused on automating network security. The slides are already online; I’ll add the link to the recording when they upload the videos.
Broadcom Expands High-End Switching Line
Broadcom's non-Trident switch chips add a few high-end options.
Cisco Virtual Router Targets Service Providers This Time
The IOS XRv counters virtual routers from Ericsson and Juniper.
DockerCon 2015 CFP Extended
Thank you to all who have submitted a session for DockerCon so far. We are very excited by the nearly 342 fantastic submissions we’ve received. After our initial call for papers closed on Monday, we received an overwhelming response and … ContinuedChoosing a Route: Order of Operations
In Cisco IOS packets are forwarded through the router (or Layer 3 switch) by Cisco Express Forwarding (CEF). A data structure called the CEF table contains a list of known IP prefixes and the outgoing interface that packets should be put on in order to get them onwards to their destination. That's well and good. But how do the IP prefixes make it into the CEF table? To answer that question you have to work backwards and understand the order of operations that IOS goes through in order for a prefix to make it into the CEF table.
EVPN Configuration
In my last blog I explained the features and use cases of the EVPN technology. In this blog I want to show how easy it is to configure, enable and expand EVPN. The configuration is focused on the Juniper MX platform, but as Junos is the single operating system across the entire Juniper portfolio, configuration on other platforms (like EX9200) is equal.
Design
The topology is really simple. I’m using 2 routers in this example, so multi-homing is not in scope. Each router has an Ethernet segment connected that consists of multiple VLANs on each side. There is 1 VLAN ID that is not equal on both sides, so this has to be taken care of.
Prepare for EVPN
To make sure we can start creating our VPN, we have to ensure the foundation is in place. This means we need IP reachability to the other Data Center routers loopback address and we need BGP with the EVPN address family enabled. The Junos release I’m testing with needs a special knob to be enabled to ensure packet lookups are done in the right way. Other versions will see this knob disappear as it is default moving forward.
routing-options {
autonomous-system 64999;
forwarding-table {
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