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Colby
Colby Glass has been in IT since 2002. He is currently a network engineer with a large Cisco partner and holds the CCNP, CCDP, CCIP, CCNA: Voice, CCNA, JNCIA-ER and ITILv3: Foundations certifications. He has also passed the CCIE R&S Written exam and is studying for the Lab exam.
Posts by Colby
Router On A Stick Tutorial
Dec 12th
Someone asked me about configuring a router on a stick yesterday, so I figured I’d make a short tutorial on it. I haven’t seen this used much in the real world as L3 switches are so common, but it is something I had to learn for the CCNA. Router on a stick is used when for inter-VLAN routing when you have an L2 switch and a router. Here’s the topology:
Here we have an L2 switch with three VLANs connected to a router. Here’s the config:
Switch
Switch(config)#vlan 5 Switch(config-vlan)#exit Switch(config)#vlan 10 Switch(config-vlan)#exit Switch(config)#vlan 15 Switch(config-vlan)#exit Switch(config)#interface FastEthernet0/1 Switch(config-if)#switchport trunk encapsulation dot1q Switch(config-if)#switchport mode trunk |
The switch config is pretty basic, we create VLANs 5, 10 and 15, then we make a trunk port to the router.
Router
Router(config)#interface FastEthernet0/0 Router(config-if)#no ip address Router(config-if)#interface FastEthernet0/0.5 Router(config-subif)#encapsulation dot1Q 5 Router(config-subif)#ip add 192.168.5.1 255.255.255.0 Router(config-subif)#interface FastEthernet0/0.10 Router(config-subif)#encapsulation dot1Q 10 Router(config-subif)#ip add 192.168.10.1 255.255.255.0 Router(config-subif)#interface FastEthernet0/0.15 Router(config-subif)#encapsulation dot1Q 15 Router(config-subif)#ip add 192.168.15.1 255.255.255.0 |
On the router, we go to the interface connected to the switch and make sure there is no IP address. Then we configure our subinterfaces with 802.1q and the appropriate VLAN. Then we give each subinterface an IP address. Now we can see all the subinterfaces are up:
MPLS and BGP Lab Guide, Part 3
Dec 9th
This is the third post in the series, the goal of the series is to provide a guide for the MPLS and BGP Lab I posted awhile back. The labs consists of MPLS VPNs and BGP along with some OSPF, NAT, IPSEC and GRE exposure. I will be posting the files needed for this lab at the bottom. Here’s the topology and the requirements:
(click image for fullsize)
Requirements:
Internet
* The two Internet routers should serve as transit ASes. No other routers should permit transit traffic.
* Internet sites (modeled by loopbacks) should be accessible by all lan IPs.
MPLS and BGP Lab Guide, Part 2
Dec 7th
This is the second post in the series, the goal of the series is to provide a guide for the MPLS and BGP Lab I posted awhile back. The labs consists of MPLS VPNs and BGP along with some OSPF, NAT, IPSEC and GRE exposure. I will be posting the files needed for this lab at the bottom. Here’s the topology and the requirements:
(click image for fullsize)
Requirements:
Internet
* The two Internet routers should serve as transit ASes. No other routers should permit transit traffic.
* Internet sites (modeled by loopbacks) should be accessible by all lan IPs.
BGP ORF Tutorial
Dec 5th
Yesterday I learned about a really interesting BGP feature that I’d never heard of. It’s called ORF (Outbound Route Filtering). With traditional filtering we have two options, filter updated in (coming from your neighbor) or out (going to your neighbor). This method works well, but there is overhead on both sides, one neighbor sending all the updates with the other neighbor filtering some or most of them. ORF is a better way of accomplishing this. Here’s the topology:
The goal of ORF is the ability of the neighbors to tell each other what prefixes they want BEFORE they are sent. This saves bandwidth and processing. For instance, R1 can tell R2 that it only cares about the 24.95.102.0/24 and 128.27.45.0/24 networks, so R2 doesn’t bother sending the 72.89.30.0/24 network at all.
Let’s get to the config:
R1
hostname R1 ! interface Loopback1 ip address 41.58.12.1 255.255.255.0 ! interface Serial0/0 ip address 10.1.1.1 255.255.255.252 ! router bgp 6505 no synchronization bgp log-neighbor-changes network 41.58.12.0 mask 255.255.255.0 neighbor 10.1.1.2 remote-as 5680 no auto-summary |
R2
hostname R2 ! interface Loopback1 ip address 72.89.30.1 255.255.255.0 ! interface Loopback2 ip address 24.95.102.1 255.255.255.0 ! interface Loopback3 ip address 128.27.45.1 255.255.255.0 ! interface Serial0/0 ip address 10.1.1.2 255.255.255.252 ! router bgp 5680 no synchronization bgp log-neighbor-changes network 24.95.102.0 mask 255.255.255.0 network 72.89.30.0 mask 255.255.255.0 network 128.27.45.0 mask 255.255.255.0 neighbor 10.1.1.1 remote-as 6505 no auto-summary |
MPLS and BGP Lab Guide, Part 1
Dec 4th
This is the first post in the series, the goal of the series is to provide a guide for the MPLS and BGP Lab I posted awhile back. The labs consists of MPLS VPNs and BGP along with some OSPF, NAT, IPSEC and GRE exposure. I will be posting the files needed for this lab at the bottom. Here’s the topology and the requirements:
(click image for fullsize)
Requirements:
Internet
* The two Internet routers should serve as transit ASes. No other routers should permit transit traffic.
* Internet sites (modeled by loopbacks) should be accessible by all lan IPs.
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