Each switching path has different capabilities when it comes to load balancing: Process switching (slowest) can only do per packet load balancing (ewww out of order packets) Fast switching (per flow) much better but not perfect CEF switching utilizes a per packet hash which results in a per flow behavior. (Can utilize per packet but …
Category Archives: CCIE R&S
1.1.b (i) RIB, FIB, LFIB, Adjacency Table
Routing information Base (RIB): AFter the FIB and adjacency tables are build, the RIB is rarely used. The only time the RIB is ever used is when packets must be processed by the routers CPU (control and management plane traffic cannot be CEF switches as they require processing). To see the RIB contents: sh ip …
Continue reading “1.1.b (i) RIB, FIB, LFIB, Adjacency Table”
1.1.b Identify Cisco Express Forwarding Concepts
Before discussing CEF one needs to be familiar with how a router actually routes a packet, these are the steps summarized: 1. Packet is received, Frame Check Sequence (FCS) is checked, if passed it moves to step 2. 2. The eth type field is is checked to indicate what the inner packet is, if 0x0800 …
Continue reading “1.1.b Identify Cisco Express Forwarding Concepts”
1.1.a (iii) Excluding Specific Platforms Architecture
IOS XE does not run on every platform. Specifically it does not run on 29xx routers, low level ISRs like the 800 or 900 series. It does run on the following though: New Catalyst 9K line Converged Broadband Routers ASR line 42xx, 43xx, 44xx ISR ISRv and CSR1000v
1.1.a (ii) Impact to Troubleshooting and Performance
IOS XE also runs a separate driver instance for each blade, thus one blade driver crashing does not crash any others that use the same driver, this is because they run their own instance of the driver. Monolithic IOS runs all of the processes in one memory space, thus if the kernel crashes or has …
Continue reading “1.1.a (ii) Impact to Troubleshooting and Performance”
1.1.a (i) Control plane and Forwarding plane
IOS-XE is able to have better logical and especially physical separation of the three planes. For example a chassis is able to have 3 blades, one dedicated to control plane, one to data plane, and one to the management plane. Granted that is a glorified example, it’s possible. Since IOS XE runs a linux operating …
Continue reading “1.1.a (i) Control plane and Forwarding plane”