Cisco – TEK@link

4 Minutes

Network

vPC vs VSS

atlink'admin March 3, 2023 0 Comment

Si l’objectif “historique” est le même : s’affranchir de la limitation de STP (blocage de ports pour prévenir les boucles), de l’usage des FHRP (HSRP, VRRP) pour équilibrer les liens, d’augmenter les performances en...

BGP Network -4 Minutes

BGP session keepalive and hold times

atlink'admin July 3, 2018 0 Comment

At the beginning of the BGP peering establishment, the BGP neighbors agree on the hold time value (included in OPEN message): the time a peering would be maintained without the reception of a KEEPALIVE...

BGP EIGRP Network OSPF RIP -7 Minutes

I-BGP synchronization with IGP

atlink'admin June 28, 2018 0 Comment

The BGP synchronization rule requires that when a BGP router receives information about a network from an IBGP neighbor, it does not use that information until a matching route is learned via an IGP...

Fabric Path Network -3 Minutes

Vlan propagation and Cisco FabricPath

atlink'admin November 21, 2017 0 Comment

PC-A and PC-B belong to the same broadcast domain that is defined by vlan X. Without FabricPath (FP), a frame that is sent by PC-A is received by FP-SW1. PC-1 MAC source address is...

DMVPN Network -4 Minutes

At the begining, … it was not DMVPN!

atlink'admin November 20, 2017 0 Comment

The simplest way to interconnect 3 or more routers in the same broadcast domain (and the same subnet) is by attaching them to a switch (or hub) in the same vlan. In case they’re...

EIGRP Network -3 Minutes

EIGRP over a vNET trunk

atlink'admin November 17, 2017 0 Comment

New IOS release 15.x introduced Easy Virtual Network (EVN) functionality to leverage some existing deployment features such as VRF-Lite and QinQ. Its ease of configuration is a real advantage. The idea is very simple:...

BGP Network -5 Minutes

VPNv4 BGP AS-Override Feature into play!

atlink'admin September 17, 2017 0 Comment

AS-Override feature applies to sites that have the same AS number and are linked by another AS number. In BGP, loop prevention would prevent any site from learning other site routes due to the...

Network OSPF -7 Minutes

Point-to-Point OSPF Network Operation over a LAN that connects multiple routers

atlink'admin August 28, 2017 0 Comment

What happens when LAN interfaces are configured as point-to-point network type OSPF interfaces instead of default broadcast type? And more than 2 ospf routers are present on this media? Let’s test this on network...

EIGRP Network -2 Minutes

DUAL route FSM Processing of EIGRP Queries

atlink'admin March 30, 2017 1 Comment

An interesting case of how DUAL route FSM operates. First let’s note that an EIGRP router send a Query to its neighbor to find a better route to a destination that has passed from...

1 Minute

Network RIP

Understand RIP Routing Timers All in One Shot!

atlink'admin March 9, 2017 0 Comment

Cisco’s RIP implementation defines 4 times tight to one periodic update interval and 3 states: invalid, hold-down and flush. The misleading information is that they are referred to as “timers” in configuration part! Apart...

Network WIFI -6 Minutes

Transmit Power Control in IEEE 802.11 Cisco WLAN networks

atlink'admin February 16, 2017 0 Comment

TPC stands for Transmit Power Control. It’s a one of Cisco RRM, Radio Resources Management, techniques that are aimed at tackling interference, cross and co-channel, in Wlan networks. RRM: TPC, CHD and DCA It works...