In my professional life at some point, I came across someone who had a stack of Catalyst 2950 switches all trunked together with their Internet routers connected to the top of the stack. This was all well and good until they kept adding hosts to the “middle” of the stack, then they had all sorts […]
If you’re running iBGP, you may have run across this. What if you had three routers — R0, R1, R2 — that were running BGP under the same ASN, but R1 and R2 weren’t peered? Any routes coming from R1 would not show up on R2 and vice versa. iBGP, by standard, does not pass […]
VLAN Trunk Protocol (VTP) is a little gem on Cisco switches that allows you configure VLANs in one place and have them appear on all of your switches. This is great for large enterprises with 8457839 switches all trunked together because who wants to configure the new VLAN for that one-off application on all 8457839 […]
A lot of IOS commands give you a lot of information. Most of the time, though, it’s way too much information, and it sure would be nice to do some grep-like stuff on the output, right? Well, just like on Linux, you can use the pipe (|) to do such. That’s not a butt cheek, […]
I realized the other day that I haven’t mentioned EIGRP once. As a Cisco guy, I think I’m required to do at least one article on it, so here it goes. Enhanced Interior Gateway Routing Protocol (EIGRP) is a Cisco-proprietary routing protocol. Routing protocols share routes, right, but “interior” is the keyword here; it’s used […]
We just talked about tagging traffic and policing traffic, but we haven’t talked about prioritizing traffic. Tagging just sets a value in the header. Policing sets a “bandwidth ceiling” that can’t be crossed. Prioritization guarantees a certain amount of bandwidth for a flow/app/etc. no matter what’s going on. Prioritization offers you a certain amount of […]
We covered QoS tagging the other day, but that just marks packets. I think you’re old enough now that we should actually do some policing. Policing is where you restrict the amount of bandwidth that a flow or set of flows can use. For example, say you have a site that serves webpages to the […]
I’ve been trying to get some experience on Cisco VOIP, and, as you probably know, Quality of Service (QoS) is quite important in that realm. Since VOIP is very time-sensitive, you have to be sure your gear delivers the voice packets first. A packet in an HTTP transaction can wait another 200ms without any problems. […]
I use Google Analytics to track the 2 or 3 hits I get a day, and sometimes I see some interesting search terms. Yesterday, some googled up the term “does the ASA 5505 run HSRP”; I think that deserves a short article. The ASA and PIX firewalls don’t actually run any of the usual HA […]
Let’s keep going with our example setup on the ASA 5505 and set up DHCP on this guy. You can set it up to either forward (relay) DHCP requests to a DHCP server somewhere or have it be the DHCP server. Let’s do it. To set up DHCP forwarding, you have to configure where the […]