Useful Ubuntu Links ….

Not particularly interesting but a few links to stop me from losing them later:

• Running Ntop on Ubuntu
• Block Control for Ubuntu
• Configure a Cut-Thru proxy on a Cisco ASA

Frame Relay Switch Configuration

Current configuration : 2101 bytes
!
! Last configuration change at 08:18:36 BST+1 Thu Sep 25 2008
! NVRAM config last updated at 08:18:43 BST+1 Thu Sep 25 2008
!
version 12.4
service timestamps debug datetime msec
service timestamps log datetime msec
service password-encryption
!
hostname FRS
!
boot-start-marker
boot-end-marker
!
!
!
resource policy
!
no aaa new-model
clock timezone GMT 0
clock summer-time BST+1 date Mar 30 2008 1:00 Oct 26 2008 2:00
clock save interval 8
no network-clock-participate slot 1
no network-clock-participate wic 0
ip subnet-zero
!
!
no ip dhcp use vrf connected
!
!
ip cef
no ip domain lookup
no ip ips deny-action ips-interface
!
frame-relay switching
!
!
!
!
!
!
!
!
!
!        
!
!
!
!
!
!
!
!
!
!
!
!
!
interface FastEthernet0/0
 no ip address
 shutdown
 duplex auto
 speed auto
!
interface BRI0/0
 no ip address
 shutdown
!        
interface Serial1/0
 no ip address
 shutdown
!
interface Serial1/1
 no ip address
 shutdown
!
interface Serial1/2
 description R2
 no ip address
 encapsulation frame-relay
 clock rate 64000
 no frame-relay inverse-arp
 frame-relay intf-type dce
 frame-relay route 203 interface Serial1/3 302
 frame-relay route 204 interface Serial1/4 402
 frame-relay route 207 interface Serial1/7 702
!
interface Serial1/3
 description R3
 no ip address
 encapsulation frame-relay
 clock rate 64000
 no frame-relay inverse-arp
 frame-relay intf-type dce
 frame-relay route 302 interface Serial1/2 203
!
interface Serial1/4
 no ip address
 encapsulation frame-relay
 clock rate 64000
 no frame-relay inverse-arp
 frame-relay intf-type dce
 frame-relay route 402 interface Serial1/2 204
!
interface Serial1/5
 no ip address
 shutdown
!
interface Serial1/6
 no ip address
 shutdown
!
interface Serial1/7
 description Connection to TS
 ip address 172.16.101.2 255.255.255.252
 encapsulation frame-relay
 clock rate 128000
 no arp frame-relay
 no frame-relay inverse-arp
 frame-relay intf-type dce
 frame-relay route 702 interface Serial1/2 207
!
ip classless
!
!
ip http server
no ip http secure-server
!
!
!
!
control-plane
!
!
!
!
!        
!
!
!
!
!
line con 0
line aux 0
line vty 0 4
 login
!
!
end

Change hostname of a Cisco CSS 11500 Content Switch

If you are wondering like I was about how to change the hostname or “CLI prompt” as Cisco seem to refer to it, of a Cisco 11500 series CSS content switch, simply use the prompt command. You don’t even need to go into global configuration mode! It’s worth bearing in mind though that if you login with a new username, the prompt will probably default back to CSS11501.

Example:

CSS11501#  prompt CSS01
CSS01#

Cisco CSS 15500 Switch

Notes on Frame Relay and ATM Configuration

Notes on Frame Relay

• Encaps the physical interface as frame-relay
• On the physical interface:
• Remove inverse arp “no frame inverse-arp” to prevent the interface from auto-discovery
• Prevent interface responding to discovery requests by turning off “no arp frame”

Point to Point FR Interfaces

• Configure the sub interface but remember to define point to point on the end
• Assign IP to sub interface
• Create DLCI map using “frame-relay interface-dlci xxx”

Point to Multi-Point Interfaces

• Configure the sub interface but remember to define point to multipoint on the end
• Assign IP to sub interface
• Map frame relay dlci’s “frame-relay map ip x.x.x.1 103 broadcast” broadcast is required for routing protocols.

Need to bear in mind that when running a point to multipoint in a hub and spoke topology, spokes are not going to be able to communicate with each other by default as the frame relay map only maps the outgoing DLCI to the IP address of the hub router.

To get to a spoke, an additional map using the same DLCI but pointing to the IP address of the other spoke is required i.e.

• “frame-relay map ip x.x.x.3 103 broadcast”. This needs to be done on ALL spokes that need to communicate with each other”

Other Useful Commands

• “clear frame-relay map” – removes any cached LMI entries
• “show frame-relay map” shows status of maps:
     active – all is good
     inactive – this end is working, the other isn’t
     deleted – this end isn’t working

With a point to multipoint environment, spokes will advertise their local networks to the hub via a routing protocol (EIGRP) but because of split horizon (not advertising something back through the interface it was received on) the advertisements will not be passed back through the interface to the spokes. Entering the following command from the multipoint sub-interface will solve the problem:

“no ip split-horizon eigrp as-num”

Frame Relay Traffic Shaping and ATM

• CIR    Committed information rate
• Tc     Timing Interval (usual 1/8 sec)
• Bc    Commited Burst
• Be    Excess Burst

CIR
—  = Bc
Tc

In the event of 64K this would be:

64000 (bits)
————  = 8000bps per time interval (clock cycle)
8

Data can only be sent through an interface at its maximum rate so if an interface is 64k, data will be sent at 8000 bps but will be forced to stop for the remaining timing intervals until its clear to send again. if there isn’t 8000bps to send, amount of data that wasn’t sent can be “banked” for use as excess burst up to the negotiated level on the next time timing interval.

Problems can arise with Excess Burst however because it can be marked by the provider as Discard Eligable (DE) which means it may be discarded during periods of provider congestion.

• BECN – Backwards Explicit Congestion Notification - will be tagged on to a return packet from the destination router by the service provider to a router that is sending data into the Frame Relay cloud at levels above their CIR and excess burst as a warning to slow down.
• FECN – Forwards Explicit Congestion Notification – A FECN is a message that is sent to a destination network by the service provider requesting the destination router to send a generic packet back to a router that is congesting the service provider network so that the service provider can tag it with a BECN flag so the sending router will slow down.

BECNS and FECNS are ignored by default.

Traffic Shaping Configuration steps

1. Create Map-Class and define parameters
2. Interface Configuration “Frame traffic-shaping”
3. Apply Map-Class to interface.

From global config “map-class frame-relay SLOW”
“frame-relay adaptive-shaping becn” – set router to respond to BECN notifications
“frame-relay min-cir 24400″ (bps) – minimum speed line will ever drop to
“frame-relay cir 28800″ – sets the CIR
“frame-relay bc 3600″ – sets the committed burst rate at 28800/8 which means 3600 bits will be sent per timing interval
“frame-relay be 200″ – sets the excess burst to 200 bits
“frame-relay tc 125″ – defaults to 125 ms which is 1/8 of a second.

“frame-relay traffic-rate 28000 200″ – does the same as above but the router will calculate the Tc Bc etc automatically.

Go into the physical interface:
“frame-relay traffic-shaping” – enables interface to support map classes (the big ON button effectively)

Then need to go into the sub interface to apply the map to the specific interface otherwise it will apply to all PVC’s
“int s0/0.1″

“frame-relay class SLOW” – apply the class

or

“frame-relay interface-dlci xxx”
“class SLOW”

“show traffic-shape”

ATM

No error checking
Has no sequence numbers
Frame size is identical for all packets – (53 bytes – 48 data/5 header)
Could be known as Cell Relay
Integrates well with other network types
Used by 80% of service providers
Variety of implementations
very Fast

“int atm0/1″
“atm pvc 56 0 115 aal5snap”

56 is a label
0 is the VPI
115 is the VCI
aal5snap is the encapsulation

Both values are locally significant.

BeBox – now a Has-BeenBox

When you sign up for a connection with UK ISP Be, they send you a router known as a BeBox to use to connect to their network. This is actually a rebadged Thomson Speedtouch device, the latest incarnation of which is the TG585V7 ….. and it’s pants.

Running the latest version of firmware which at the time of writing is 7.4.20.3, the router reboots itself on a regular basis, resyncs for no apparent reason and randomly shuts down the wireless interface. These problems don’t appear to be limited to the V7 device, there are reports in the forums of users with earlier V6 boxes experiencing the same or very similar issues.

To work around the problem, I’ve laid my hands on a Draytek 2820 router and a separate Linksys 54G WAP and touch wood, everything appears to be fine at the moment. I have a Cisco 1130AG accesspoint at the office which I plan to bring home at some point but for now, I’ll keep monitoring the connection and see what happens.