Cisco and Networking

Post regarding Cisco and general networking issues and their fixes.

HP BladeSystem Flex 10 Ethernet Switch Configuration

posted 19 Aug 2016, 07:46 by Tristan Self

Had to do a bit of configuration on an HP c7000 blade chassis the other day. There was a need to have two separate uplink pairs going to two different pairs of switches from the single chassis. I needed to provide both uplink paths to each host within the chassis (they were ESXi hosts).

Here is the configuration to do this for one of the uplink pairs, for the other uplink pair you just do the same thing, but applying the server-port-map-range to different physical ports on the blade. Each blade has 8 pNICs (4 on the LOM and 4 on a mezzanine card).

In this example ports 3 and 4 are going to be used to provide active/standby paths through the Flex-10 fabric to the physical network beyond.

add uplinkset VLAN_Trunk_1 ConnectionMode=Failover
add uplinkport enc0:1:X4 UplinkSet=VLAN_Trunk_1 Speed=Auto Role=Primary
add uplinkport enc0:2:X4 UplinkSet=VLAN_Trunk_1 Speed=Auto Role=Secondary

add network vlan1 -quiet UplinkSet=VLAN_Trunk_1 VLanID=552 NativeVLAN=Enabled NAGs=Default
set network vlan1 SmartLink=Enabled

add network vlan2 -quiet UplinkSet=VLAN_Trunk_1 VLanID=555 NAGs=Default
set network vlan2 SmartLink=Enabled

add network vlan3 -quiet UplinkSet=VLAN_Trunk_1 VLanID=554 NAGs=Default
set network vlan3 SmartLink=Enabled

If you want vlan1 to be untagged to the host where these 3 vlans are trunked to the host on ports 2 and 3, you need an extra bit of configuration:

set server-port-map serverprofile1:3 vlan1 untagged=true
set server-port-map serverprofile1:4 vlan1 untagged=true

Cisco ASA Firewall - DMZ to Inside Access

posted 15 Jul 2015, 09:13 by Tristan Self   [ updated 15 Jul 2015, 09:26 ]

On a Cisco ASA firewall you will probably want to use the DMZ for servers that are web facing, and also restrict/deny any access they have to the internal network. The idea being that a connection to a web server say in your DMZ would get into the DMZ, and if another connection is required e.g. for a database lookup, it would be made back through the firewall between the DMZ and inside to the internal server.

When a firewall is brand new and un-configured, there is an implicit incoming rule on the interface saying "any less secure networks" so this means that if you have configured the interface security levels as follows:

outside = 0
inside = 100
dmz = 50

then the following is true:

A host on the inside (internal network) can access anything on the dmz or outside (internet) using the default implicit rules.
A host on the dmz (DMZ network) can access anything on the outside (internet) but not the inside (internal network) using the default implicit rules. Because it only allows "any less secure networks".

But at the point of adding your own rules to the ACL this implicit rule is removed and then an implicit deny is added to the end, and then only your traffic is allowed.

So onto the point of this article. A scenario to explain it all.

If you have a host on your DMZ network and you want it to only be allowed to access the internet on HTTP or HTTPS (i.e. DMZ to outside) and allowed access to the internal network on TCP/1433 (SQL) (i.e. DMZ to inside) you need to setup the commands below.

The rule set is basically split into 4 sections below to allow traffic to the inside host from the DMZ, traffic from the DMZ to the internet, block all other traffic from the DMZ to the inside and block anything else.

1. Allow specific traffic from the DMZ to the inside.access-list dmz_access_in line 1 extended permit tcp host object inside-network eq sqlnet
2. Deny all other traffic from the DMZ to the inside.access-list dmz_access_in line 2 extended deny ip host inside-network
3. Allow specific traffic from the DMZ to the outside.

access-list dmz_access_in line 3 extended permit tcp host any4 eq http

access-list dmz_access_in line 4 extended permit tcp host any4 eq https

4. Block Everything else.access-list dmz_access_in line 5 extended deny ip any any

Cisco ASA NAT Exemption (post version 8.3)

posted 13 Jul 2015, 08:52 by Tristan Self

The changes to the ASA IOS post version 8.3 changes the way that NAT works. NAT Exemption is normally used to disable translation for certain addresses e.g. for VPN tunnelling.

So for this example below you create an access-list containing the IP addresses that are to be exempted from NAT. So say these are the site to site VPN addresses where is the A end, and is the B end.

# access-list NAT_EXEMPT extended permit ip
# nat (inside) 0 access-list NAT_EXEMPT

This basically says traffic going through the firewall from to through the firewall should not be NATTed.

Cisco ASA Static NAT (pre version 8.3)

posted 13 Jul 2015, 06:35 by Tristan Self

Pre version 8.3 to statically NAT an internal host to an external IP address you would use the following:

 static (inside,outside) netmask

This then means......

inside = the source interface for the NAT connection (assuming going from the inside to the outside)
outside = the translated interface for the NAT connection = External IP address to which the internal host is translated to on the outside. = Internal IP address from which is the original source of the traffic.
network mask = Specfies that it is a single host, change this to for a range of addresses for example.

Cisco ASA Dynamic NAT Example (Post version 8.3)

posted 10 Jul 2015, 08:45 by Tristan Self   [ updated 13 Jul 2015, 08:29 ]

Okay a basic example with a Cisco ASA for the NAT rules. Lets say there is PC1 on the inside network that you want to have internet access. The IP address can't just connect to the Internet using that IP address as its not routable, so instead we need to translate it. 

In this example the PC1 is going to be translated from the IP address to (the IP address of the outside interface of the Cisco ASA firewall), to make its outgoing connection. On the way back in the translation is made in reverse, so the traffic coming back from the webhost goes back to, a dynamic translation is in place (in memory) on the firewall that translates this back to the original IP address

Now thats fine for one PC but what about a whole network of PCs sharing one IP address, you can't have this for each you'd run out of IP addresses on the outside interface. So instead, you add a port number (hence the dynamic NAT or PAT, port address translation), this ensures that each individual translation can be uniquely idenified by a port number so that it can find its way back. Right lets go through that example above again with PAT.

PC1 is going to be translated from the IP address to (the IP address of the outside interface of the Cisco ASA firewall), to make its outgoing connection. On the way back in the translation is made in reverse, so the traffic coming back from the webhost goes back to, a dynamic translation is in place (in memory) on the firewall that translates this back to the original IP address

PC1 ( -----> (inside) <-----> ASA Firewall <-----> (outside) --------> WebHost


Okay so how do you configure this, well you create a network object for the internal range (i.e. the range PC1 is in) so, then you put the NAT rule within it so something like this:

 object network inside-network
    nat (inside,outside) dynamic interface

Okay so what does this mean? Well you create the object network inside-network then say its the subnet At this point you then apply the dynamic NAT (PAT) rule to the network object that says any traffic hitting the inside is translated to the outside using dynamic NAT (PAT) on the firewall's outside interface IP address. Of course here if you have more than 1 IP address on the outside firewall port you could use one of these in the rules instead.

inside-network = the internal network object name

subnet = the subnet definition

nat (inside,outside) = the source interface (i.e. inside) and the destination interface (i.e. outside) of the translation

dynamic = specifies that this is a dynamic NAT rule as opposed to a static NAT rule.

interface = specifies to use the outside interface's IP address in this example, here you could substitute a specific IP address if you didn't want to use the firewall's interface IP.


You'll also need an access control list rule to allow this out, so a quick example that would allow port 80 HTTP out to any IPv4 address on the internet would be something like this:

 access-list acl-in extended permit tcp object inside-network any4 eq 80

acl-in =  Means the ACL on the inside firewall (so traffic coming into the inside interface going to the outside or dmz interfaces).

tcp = Means the type of traffic TCP or UDP, in this case TCP for TCP/80 HTTP.

inside-network = Means the source network or host (as an object in this case).

any4 = Means the destination network or host (in our case this is any host on the Internet).

80 = Means the destination port on the remote host (in our case HTTP port TCP/80).

Pre version 8.3

Create the pool for the outside interface:
 global (outside) 1 interface

Now create the dynamic NAT (PAT) rule for all inside traffic to the outside

nat (inside) 1

This is all you need from a NAT point of view, now you can create an ACL to allow out the traffic.

Enable Wake On Lan Across VLAN on Cisco Network

posted 6 Feb 2015, 04:47 by Tristan Self

Wake on LAN packets do not traverse routers (normally) so you need to configure your network to do this. There are some security implications you need to be aware of first, Cisco's document on it is a good read:

Also download Solarwinds Free Wake On LAN tool, its a good one to use to test this, it also has a command line to it as well.

So in this example we have the Wake On LAN controller PC on the IP address in VLAN 240. The PC(s) we want to switch on are in the VLAN 244 subnet. We need to configure our core switch/L3 router with the below. This will allow the controller PC to send a request to the subnet to wake up the PC.

access-list 150 permit udp host any eq 7
ip forward-protocol udp 7
interface vlan 240
 ip helper-address

interface vlan 244
 ip directed-broadcast 150

You need to ensure that the WOL tool you are using will send on udp port 7, if it doesn't the IP directed won't match.

Set the TFTP Source Interface Cisco Switch

posted 18 Jul 2014, 03:21 by Tristan Self

This was an interesting one, I was trying to download a IOS image to a switch but the connection was being denied.

It turned out the connection was coming from a VLAN interface on the switch that did not have access to the TFTP server.

You can force the VLAN interface used with this command:

ip tftp source-interface vlan 5

Where the VLAN 5 is the interface from which the want the traffic to emerge.

Cisco ASA https:// Page Cannot be Displayed

posted 21 May 2014, 02:18 by Tristan Self   [ updated 21 May 2014, 02:20 ]

Okay here's a weird one, we had two identical clusters of firewalls running:
ASA IOS: 9.0(2)
ASDM: 7.1(2)
One of the firewall clusters you could access https:// to get to the ASDM with no problem, the other one, you access you get page cannot be displayed with some error about SSL not working.
Firstly I ran this command:
# show run all ssl
ssl server-version any
ssl client-version any
ssl encryption des-sha1
Note the bottom line in green, this only has one type of encryption strangely you'll find this works on Windows XP and not Windows 7. You need to run this command from the command line to enable it:
# ssl encryption rc4-sha1 aes128-sha1 aes256-sha1 3des-sha1
Now if you try to access https://<ip of firewall> you should find it works. Note you also need to be sure you are running the correct version of Java too.

Cisco 3750 and 3750e in a Stack

posted 30 Jan 2014, 04:18 by Tristan Self

Here's something that came up, we are replacing a few switches and want to replace it will a couple of 3750s and a 3750e in a stack.

The issue was that the 3750e has a different IOS to the 3750s but still must be the same version. After some playing around I found these versions work together.


This is the latest version that the 3750 (v1) supports, it won't support the 15.0 IOS because the flash isn't big enough. The 3750e can't run anything lower than this because its firmware is not compatible.

But this has allowed me to get two 3750s and a 3750e working in the same stack with no problems.

Using IPv6 (Part 1)

posted 20 Jun 2013, 04:01 by Tristan Self   [ updated 28 Jun 2014, 03:46 ]

Although IPv6 is still fairly unused in the enterprise or home, it is beginning to gain traction, so I thought I should begin to learn about it. These articles there will be a few will chart my investigations into setting up IPv6, starting in this part with two workstations on the same network segment and also connecting them to an IPv6 website on the internet.

I'm not going to explain about what IPv6 as you can find pages of information of this on the Internet, i'm looking at it from the more practical (useful) side about how you can use IPv6 in practice and setup a network to use it.

At the moment there are a few ways that you can use IPv6, the most important ones are:

1. IPv6 native, you use IPv6 natively, your hosts on your network are IPv6 only, you connect using IPv6 compatible routers and firewalls to IPv6 websites, not all sites are IPv6 yet so you might find large parts of the Internet are not available to you. (See section 1 below)

2. Dual Stack (IPv6 and IPv4) - Having both stacks running on the same host gives you the best of both worlds, but adds to the complexity, you have IPv6 enabled, but the IPv6 component must tunnel across the IPv4 devices and networks if it doesn't support IPv6. (See section 2 below)

3. Some sort of tunnel broker that will tunnel traffic across the IPv4 networks, similar to the Teredo type thing that Microsoft offers in Windows. Except you could get your edge router to tunnel out to the IPv6 Internet, even if your Internet connection and ISP is only IPv4.

1. Two Windows 7 Workstations on the same network segment (VLAN)

Okay this is a basic proof of concept test. I have two computers connected to the same VLAN on my network, both run Windows 7 and i've turned on the IPv6 IP stack.

Firstly run IPCONFIG to get the details of the IPv6 connection:

> ipconfig /all

Now from this you can see the IPv6 IP addresses are as below, if you repeat for workstation 2, you'll see that the addresses are different, but start with "fe80" this means it is a link-local address. I.e. one you can use to access the Internet. In IPv6 a host may have mulitple IPv6 addresses, one to connect to other local hosts, one to connect to internet hosts and so on.

Workstation 1: fe80::75c7:d95b:1f7e:65ce
Workstation 2: fe80::949f:66d7:ca65:6668

Now lets do a ping from workstation 1 to workstation 2, and see what happens, note I've added the %11 at the end of the IP address, this signifies the interface I want the connection to go out of, if you don't specify this you may find you can't ping and it tries to resolve the IPv6 address as a hostname.

There we go its working, we can ping from one to the other. You'll notice that this address has been auto selected, we don't have an IPv6 DHCP server (yet) so this link-local is being auto-configured by the PC on the network automagically.

Once of the odd things with IPv6 is you don't need to have a DHCP server, IPv6 is more about the auto configuration of hosts, but i'll come onto this more in the end.

2. Connecting a Windows XP or Windows 7 workstation to an IPv6 website on the Internet using Teredo

Okay so how about now using it on the Internet to access a host off your network, well unless you have IPv6 networking all the way from your internal computer to the web server somewhere on the internet you'll struggle. Microsoft provide within Windows XP and 7 (Vista, cough) the Teredo adapter, you might have seen this when you did an IPCONFIG.

Right so in this example, I have my Windows XP SP3 host on my internet network, I want to be able to connect to an IPv6 website, say:, if you try and access it on a IPv4 only host you'll not be able to access it, so you need to enable the Teredo adapter.

This will tunnel any IPv6 requests into a tunnel across the IPv4 network and Internet (through any NAT devices, like your network firewall) to a Teredo Relay that will then spit the the traffic out onto the IPv6 Internet for the last mile connection to the IPv6 webserver. The return traffic going back to the Teredo Relay and through the tunnel back to your host.

1. First up you need to make sure that port UDP/3544 is open outbound through your firewall to the Internet, if its not, you won't be able to use the Teredo tunnel. I use a Cisco ASA firewall so you'd need something like this:

access-list acl_in line 84 extended permit udp object-group OAKLANDS any4 eq 3544 
access-list acl_in line 83 remark Allow outbound traffic on UDP/3544 to the Internet for use of Teredo IPv6 Client.

2. Now you need to setup your PC, i'm using Windows XP SP3, the settings are basically the same for Windows 7, except you don't need to add the IPv6 interface.

3. Add the IPv6 protocol to your interface. Control Panel  then Network Connections -> Right-Click “Properties” on your LAN or Wireless connection, “Install…”, “Protocol”, “Add…”, choose “Microsoft TCP/IP version 6″, hit “OK” until all the windows are closed.

At this moment, the IPv6 is enabled, and will decide upon a link-local address of its very own. You can have a look at it with ipconfig /all if you want, but we are not done yet, this link local is no good for accessing things out on the Internet.

4. Right now you need to make a few changes on XP, again you might not need to, the modification of Windows XP Teredo clients can be done with any of the folowing two ways:

4A) Installing the Windows Update KB922819. Note that if you have installed the Peer Name Resolution Protocol (PNRP), which is available in the Windows Update KB920342, then you do not need to install the KB922819 update.

In my case I did option B, because I was running SP3, these two patches above are already installed.

4B) Adding or altering the REG_DWORD value of the \HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Tcpip6\Parameters\GlobalParams\TeredoPrefix entry in the Windows Registry. The REG_DWORD value is interpreted as a 32 bit prefix, in network byte order. To do that just follow the following steps:

i) Run the regedit.exe program: Start -> Run -> Write regedit.exe and then click on OK button.
ii) Browse through the registry tree to check if the


      entry exists. If don't so, add it.
iii) Add/modify the REG_DWORD value to 0x00000120 (288).
iv) Reboot your system.
v) Follow the configuration guides for Windows XP/ Windows 2003 below for configuring your Windows Teredo Client.

If you are on:

On Windows 7 Business and better:

  • Run “gpedit.msc” from the Start Menu by typing it into the search bar or “Run” bar.
  • Navigate to Computer Configuration -> Administrative Templates -> Network -> TCPIP Settings -> IPv6 Transition Technologies
  • Double click the “Teredo Default Qualified” setting, change it from “Not Configured” to “Enabled”, and click OK, then close gpedit.msc.
  • The setting should take effect rather quickly, but you can do “gpupdate /force” to force a refresh.

5. Right, reboot and log back in and then fire up a command prompt. First thing to do is setup the Teredo client to use a Teredo relay, in my case im using one in France as this is closest, but there's some all over the place, so take your pick. (France)
      It provides the new 2001::/32 prefix. (Spain)
      It provides the new 2001::/32 prefix. (USA, Redmon)
      It provides the new 2001::/32 prefix. (NCA, Korea)
      It provides the new 2001::/32 prefix. (Australia)
      It provides the new 2001::/32 prefix.

 > netsh interface ipv6 set teredo client

6. Now, my machine was on a domain, so you also need to run this command too:

> netsh interface ipv6 set teredo enterpriseclient

7. Right we are ready, so now run this command to see if your tunnel has come up:

 > netsh interface ipv6 show teredo

7. Okay it appears to be working, next we'll check our routing, run this:

 > netsh interface ipv6 show route

8. Okay this also looks good. Right now we can do a ping test. as below:

9. Using IE, we also get:

10. We are done, we are using an IPv6 website via an Teredo tunnel over an IPv4 network and internet connection. Obviously this is just step one in to my investigation of IPv6, so more will come but it does show that we can use IPv6 is some form. Next I will investigate further into how to begin the migration of our network and hosts over to IPv6 and if its even possible.

11. And for interest, here is the IPconfig when connected, you can see now we have our IPv6 IP addresses:

Link-Local: fe80::21a:a0ff:fe5e:61be
Global (via Teredo): 2001:0:53aa:64c:0:f9f8:2b24

You can always, run an IPv6 test using a website link: this will allow you verify you IPv6-ness.

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