Category: Cisco

IPsec VPN Mikrotik to Cisco

Not long ago I wrote an article on how to configure an IPsec VPN using Mikrotik and Linux devices. For today, I will replace the Linux device with a Cisco. I did test the entire construct in GNS3 integrated with Mikrotik.

The topology looks like this:

IPsec VPN Mikrotik Cisco

The red line represent the IPsec VPN tunnel.
Please note the used IP addresses. In this way the below configuration will be easier to understand.

Mikrotik Configuration

1. Firewal rules

By default, the Mikrotik comes with the INPUT channel that drop the connection incoming on ether1-gateway (which is the WAN interface). You need to be sure that at least the IPsec packets are able to be accepted inbound on the WAN interface, so the below rules needs to be placed before the rule dropping packets (the Firewal rules are checked top-down)

On INPUT channel allow the following on the interface facing Internet
– Port 500/UDP
– Port 4500/UDP
– Proto 50
– Proto 51
It may be that you don’t need all these ports, but you can close them later. You can check logs if you want to troubleshoot.

On NAT channel, SRCNAT you need have the rule involving interesting traffic (local LAN subnets for example) before NAT masquerade.
You need to add a rule with ACCEPT source LOCAL_LAN (192.168.88.0/24 in this example) destination REMOTE_LAN (192.168.0.0/24 in this example).

On Console the configuration looks like this:

CLI

2. The IPsec Proposal

GUI

IP > IPsec > Proposals

CLI

3. The IPsec Policy

GUI

IP > IPsec > Policies

CLI

4. The IPsec Peer

GUI

IP > IPsec > Peers

CLI

Cisco configuration

1. Crypto ISAKMP Policy

You can specify also the hash as sha1, but this is the default method on Cisco, so no extra line will appear.

2. Crypto ISAKMP neighbor

3. Crypto IPsec transformation set

4. Crypto map

5. Access-list for interesting traffic

6. Interface config

The settings (like encryption algorithm) can be tuned to fit your requirements.

If you have any questions or something is unclear please let me know in Comments.

GNS3 1.2.1 installation on Ubuntu 14.04

As mentioned in an earlier post GNS3 is moving ahead fast. Currently at version 1.2.1 the GNS3 is looking great. Compared with the version 1.0 Beta 1 which I had installed, the 1.2.1 is not only more stable, but it has the Menu more clean and compact. For example now there is only one Preferences menu where you can adjust all your settings.

During the installation of 1.0 Beta 1 I made some notes in Evernote and it prove to be very useful as the installation was pretty messy. With 1.2.1 I did the same thing, but the installation was very smooth. Still, I said that if I made those notes maybe I should share them for those interested in a quick installation. A more complete guide can be found on GNS3 Community.

1. Download GNS3 1.2.1

Head over to http://www.gns3.com/, create and account and download the bundle archive for Linux.

If you for some reason you don’t want to create an account, you may download each package individually from https://github.com/GNS3

The following lines will assume that you have the bundle archive.

2. Install Ubuntu 14.04 dependencies

3. Unzip the bundle archive

You should see 5 packages in GNS3-1.2.1 folder:
dynamips-0.2.14.zip
gns3-server-1.2.1.zip
gns3-gui-1.2.1.zip
iouyap-0.95.zip
vpcs-0.6.zip

4. Install Dynamips

To check if the correct version is install:

You should see in the output 0.2.14

5. Install GNS3 Server

To check if the GNS3 Server is installed correctly:

If you see some output other than an error, than you’re fine.

6. Install GNS3 GUI

To test if the installation is working:

You should see a graphical interface of GNS3 launched.

At this moment you have a working GNS3 environment if you want only want to test Cisco hardware emulators. I strongly recommend to continue and install also the rest of the components. Who knows when you’ll need them

7. Install IOUyap (Optional, if you will use IOU images)

To test the installation:

If you encounter an error, please check the [Update 1] section at the bottom of this article.

8. Install VPCS (Optional, if you want to use VirtualPC)

For the third line, the 64 represent 64bit, as my Ubuntu 14.04 is build on 64bit.
The values can be:
– 32 or i386 for 32bit OS
– 64 or amd64 for 64bit OS

Please be sure to use the correct one for your OS.

To test the VPCS:

You should see a Virtual PC being launched. Leave the console with letter q.

9. Install VirtualBox (Optional, if you want to launch VMs)

Download the correct version for your system from https://www.virtualbox.org/wiki/Linux_Downloads. The following lines will assume an Ubuntu 14.04 64bit OS.

You can also use the instructions at https://www.virtualbox.org/wiki/Linux_Downloads and go for an APT installation.The choice is yours.

10. Install Qemu (Optional, if you want to use qemu images)

11. Install IOU (Optional, if you want to use IOU images)

I’m not a legal matter expert, and the usage of IOU is sort of grey area. Because of this, I’m not going to cover this chapter.

You’re ready to go. Start the GNS3 GUI:

Some things to check before going live:

  • check in the menu Edit > Preferences to set your desired Paths (in General sections) and to check the paths for the binaries (dynamips, vpcs, iou, virtualbox…)
  • add the IOS, virtualbox vm, iou images
  • in case of Cisco hardware emulators don’t forget to find the IdlePC value (when you add the IOS image or later with the start of your first router with a certain image) otherwise your CPUs will cry.

If something does not work as described or you need help please let me know in Comments.

[Update 1]

If you get the following error during installation of iouyap:

Try to install the iniparser as follows:

then

and finally iouyap

Thanks to mweisel @ forum.gns3.net for this update!

Cisco BGP soft-reconfiguration and received-routes relation

A while ago I received the following question:

“Why I’m not seeing the prefixes received from the BGP peer when using the show ip bgp neighbors x.x.x.x received-routes while the soft-reconfiguration inbound is not enabled?”

I must admit that I had to stop and think for a second before giving my response.

Simple BGP

For the above diagram I have a simple BGP configuration:

Focus is on the secondary router. I’m trying to see what prefixes I receive from my BGP neighbor, so I rapidly hit the following command:

OK, that’s not good. Am I missing the command? Let’s see:

-> received-routes – Display the received routes from neighbor

OK, I know the soft-reconfiguration inbound is not enabled, but what has this to do with the fact that the command is not showing me what routes I receive from BGP neighbor?

Let’s recall what “soft-reconfiguration inbound” command actually does.

BGP soft-reconfiguration inbound
*Cisco BGP-4 Command and Configuration Handbook

According to the above explanation, if you have an inbound policy (like a route-map) applied to a BGP neighbor and you change that policy, you need to clear the BGP session before it take effect. This is the procedure without having “soft-reconfiguration inbound” configured. I remember it like this and most of the network engineers out there remember this behavior associated with the “soft-reconfiguration inbound” command.

Still, I just want to see what routes I received from BGP neighbor and according with “sh ip bgp neighbors 192.168.0.1 received-routes” description is the right command . I have no inbound policy on R2 for R1 BGP neighbor.

A less remembered fact about the “soft-reconfiguration inbound” command is that when added, the router begins to store updates from the specified neighbor. These updates are unmodified by any existing inbound policies so that the router can correctly apply the new policies when soft reconfiguration is triggered.

Where are these updates stored?

In the BGP Adj-RIB-in (Adjacent Routing Information Base, Incoming) table. So, what the “received-routes” command does actually is looking in the BGP Adj-RIB-in table for the received routes from the BGP neighbor. I consider that the “received-routes” command has an ambiguous explanation leading to confusion.

When “soft-reconfiguration inbound” is not present, the BGP router does not store anything in Adj-RIB-in. Rather it process the update and discard the Adj-RIB-in table, but not before adding the information in the Loc-RIB (Local Routing Information Base) table. Knowing these facts of course the BGP router returns an error when trying to check the received prefixes using the “received-routes” command.

To check actually what’s received from BGP peer and stored in the Loc-RIB (after being processed by inbound policies) use only the “routes” parameter in the command:

-> routes – Display routes learned from neighbor

The output is what exists in the Loc-RIB table, after processed by the inbound policy.

Let me show you an example of the above explanation.

I’ll apply the “soft-reconfiguration inbound” first:

Now I’ll check again the received routes:

OK, so I have three prefixes, reflected in the Adj-RIB-in table.
Checking next the Loc-RIB tables (so the routes installed after being processed by inbound policies):

The Adj-RIB-in and Loc-RIB tables are identical.

Now, I’ll apply an inbound policy that will filter the 3.3.3.3 prefix.

OK, we have the “soft-reconfiguration inbound” in place, so the inbound policies should be applied automatically denying the 3.3.3.3 prefix.

The above output is what we receive from BGP peer. Notice that the 3.3.3.3 prefix is still there, in the Adj-RIB-in table, as the inbound policies are not applied yet. The only visible change is the missing > sign (best).

Now we can see that the inbound policy is working fine as the 3.3.3.3 prefix is not installed in the Loc-RIB table. This is also the explanation why the > (best) sign was missing from the 3.3.3.3 prefix in Adj-RIB-in.

I hope you understood the logic behind the confusion which these commands “received-routes” and “routes” and their explanation in IOS is creates.

Please let me know in Comments if you have any questions.

EGP

Today I came across an old Cisco router with original IOS image. Big surprise (at least for me) when I did check what routing protocols are supported on this router:

EGP protocol

I was out of the game, or better not even yet had discover the networking games, when the EGP was still out there and available to be configured on the Cisco routers.

I hope to bring a smile on your face or some nostalgic memories when you’ll see this :)

Cisco switches and smartport macros

Smartport macros are not more than some templates you can define on Cisco switches that will apply the same configuration on multiple ports. It’s not a subject that needs too many discussions, but it can be useful for your Cisco certification preparation or real life Cisco switch administration.

Configuration is very simple and it goes something like this:

After this you apply the macro to a port or a range of ports:

That’s it :)

A less known fact is that Cisco switches are having some predefined smartport macros, which can be really helpful. The smartport macros which you configure can be spotted with a simple “show running-config” command. This is not the case for the default smartport macros which cannot be seen in the running-config, so you may not be aware that they exist.

The default smartport macros can be seen using the following commands:

This will show you only a summary of the default smartport macros. If you want to see what are they configure to do, check the following command:

To be honest I never used them like this, but they were a pretty good starting point to customize new smartport macros.

If you are rather interested in the Cisco switch interface macro command, I did write a post on this topic some years ago and you can read it here.