In this blog we’ll take a look at different protocols for gateway redundancy. So what is gateway redundancy and why do we need it? Let’s start with an example!
Here’s the topology we will use:
GLBP stands for Gateway Load Balancing Protocol and just like HSRP / VRRP it is used to create a virtual gateway that you can use for hosts.
One of the key differences of GLBP is that it can do load balancing without the group configuration that HSRP/VRRP use (what’s in a name right?).
Let’s take a closer look:
IP SLA (Service-Level Agreement) is a great feature on Cisco IOS devices that can be used to “measure” network performance.
This can be something simple like a ping where we check the round-trip time or something more advanced like a VoIP RTP packet where we check the delay, jitter and calculate a MOS score that gives you an indication what the voice quality will be like.
IP SLA is a great tool on Cisco routers that allows us to generate traffic which can be used to check delay/latency, jitter but can also be combined with object tracking. This allows us to check the reachability of a certain IP address (by pinging) or a certain service by connecting to it (using TCP). If the IP address/service is unreachable we can apply a certain action. A simple example to demonstrate IP SLA is when you have a single router that is connected to two ISPs:
RIP is a fairly simple protocol and most CCIE R&S students don’t worry about it too much. There are however a number of ‘pitfalls’ that you need to be aware of. One of them is configuring RIP to advertise a default route in combination with IP SLA and object tracking. We will discuss how to do this with the following three routers: