BGP Dampening

BGP route dampening can be used to reduce the propagation of unstable routes throughout a network. When a prefix flaps it will be assigned a penalty of 1000 and moved into the dampening state “history”. Each flap incurs another penalty (of 1000), which is applied cumulatively. If the penalty reaches the suppress-limit, the route is dampened, meaning it won’t be advertised to any neighbors. The default values for each dampening criteria are stated below:

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Active-active router redundancy using VARP

In most of Leaf-Spine deployments, redundancy in Spine layer is required to achieve high availability and to prevent network service disruption. Modern layer 2 networks adopted loop-free and balanced path networks using Multi Chassis Link Aggregation topologies with LACP port channels, leaving loop control methods (STP) as second protection layer. Spines also supports layer 3 networks, using ECMP in a scalable network topology. For unicast redundancy in layer 3, a common method is use First Hop Router Redundancy (FHRR) to provide a simple and unique gateway for Leaf level. VRRP and HRSP are popular FHRR protocols and supported in most equipments today. Although HSRP and VRRP provide redundancy, they are active-standby FHRR protocols and do not provide a balanced data traffic distribution over Multi Chassis Link Aggregated topologies. The following figure show show data traffic is handled using active-standby FHRR protocol topology.

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What Does DOM Mean for a SFP Transceiver?

If you take a look at the description of a SFP transceiver module, you will see the “DOM support” appeared in the product details. What does it mean? In fact, DOM or Digital Optical Monitoring as the words implies, is used for monitoring some parameters of the transceiver, which can help to identify the location of the fiber link failure, simplify maintenance, improve system reliability. Obviously a SFP with DOM function is high-ender than one without it. This is why most of modern optical SFP transceivers support DOM functions. To have a further understanding of DOM, some detailed information will be introduced in the following passage. Continue reading

EIGRP Wide Metrics

First and foremost, the metric has been reworked.
EIGRP named mode automatically uses wide metrics when speaking to another EIGRP named mode process. No additional configuration is necessary, this is automatic. So if it’s speaking to a traditional EIGRP process, it uses the old calculations.

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IOS Conditional Debugging

I while back I mentioned it is possible to debug a single IPSec tunnel using crypto conditions, this functionality also extends outside of crypto conditions. IOS routers offer the functionality to create debug conditions and limit debug output to specific interfaces, ip addresses, and more see the following list:

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How To Calculate Optimal TCP Window Size For Long Distance WAN Link

If you have a requirement to copy large amounts of data along way around the world you may find that despite your link being 60Mb/s if it’s 5,000 miles away you only can transfer files at much less like 10Mb/s. The cause of this is generally the TCP Window Size is optimized by OS and FTP clients by default to work on networks with less distance and less network round trip latency. Continue reading