BSCI becomes ROUTE
BCMSN becomes SWITCH
ISCW and ONT become TSHOOT

Looks like more IPv6 content, multicast and IS-IS are gone, and more focus on simulations and troubleshooting.

The old exams are phased out on July 31, so if you have can make it by that date, get cracking!

Exams are now $200.

Content Copyright Sean Walberg

CCNP completely redone

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Router> enable
Router# conf t
Router# access-list 100 permit tcp any any eq ?

This will result in the following table:

 <0-65535>    Port number
bgp          Border Gateway Protocol (179)
chargen      Character generator (19)
cmd          Remote commands (rcmd, 514)
daytime      Daytime (13)
discard      Discard (9)
domain       Domain Name Service (53)
echo         Echo (7)
exec         Exec (rsh, 512)
finger       Finger (79)
ftp          File Transfer Protocol (21)
ftp-data     FTP data connections (used infrequently, 20)
gopher       Gopher (70)
hostname     NIC hostname server (101)
ident        Ident Protocol (113)
irc          Internet Relay Chat (194)
klogin       Kerberos login (543)
kshell       Kerberos shell (544)
login        Login (rlogin, 513)
lpd          Printer service (515)
nntp         Network News Transport Protocol (119)
pim-auto-rp  PIM Auto-RP (496)
pop2         Post Office Protocol v2 (109)
pop3         Post Office Protocol v3 (110)
smtp         Simple Mail Transport Protocol (25)
sunrpc       Sun Remote Procedure Call (111)
syslog       Syslog (514)
tacacs       TAC Access Control System (49)
talk         Talk (517)
telnet       Telnet (23)
time         Time (37)
uucp         Unix-to-Unix Copy Program (540)
whois        Nicname (43)
www          World Wide Web (HTTP, 80) 

Content Copyright Sean Walberg

Checking common port numbers on Cisco IOS

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I’m giving 2 talks on using Wireshark to expose VoIP problems at Sharkfest ‘08 (schedule). Details are sketchy, I think one of the talks is more of a hands on lab, the other is me talking. I’ve expanded on my techniques from the Linux Journal article I wrote on the topic.

Some other fascinating topics going on at the same conference, especially wireless analysis and performance monitoring. Hope to see you there.

Content Copyright Sean Walberg

I’ll be speaking at Sharkfest ‘08

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Content Copyright Sean Walberg

Bye bye Prometric…

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Laying the groundwork for more rigorous certification, CCENT validates the knowledge and skills needed to configure and verify small routed and switched networks, including the ability to configure IP addressing, implement basic security measures and understand the concepts of wireless networking.

Cisco Press, of course, has both new CCNA and CCNENT books on the way. For those that will be doing their studying during this transition and already bought books, using the Digital Short Cuts would be cheaper than buying new books. (I previously looked at a couple of PDF based products)

A cursory look at the new CCNA exam shows that the trend of migrating content from the CCNP stream into the CCNA stream is continuing. I see some basic IPv6 and Wireless, DHCP, and security topics in there, and some more details on switching protocols.

If you don’t want to take the one big exam, you take both ICND1 (640-822) and ICND2 (640-816). Last day to test the old exams is November 6th, with the new exams coming out August 1st.

I’m always in favour of raising the bar on certifications, though I’m not sure how much traction this CCENT certification will get seeing as it’s a stepping stone to an already entry level certification. However, if it helps get more people into the game, I’m all for that.

Content Copyright Sean Walberg

More exam changes for the CCNA track

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My CCNP expired a couple of years ago. I started this website so that I could post my study notes for the recert exam and hopefully help others.

A few months into that, I got the opportunity to write a book which I took. This unfortunately caused me to miss my deadline, so my CCNP was then invalid.

My agent from my book also got me into writing about UNIX for various parties, which slowed down the pace of my recertification. Eventually I got my CCNA again, and BCMSN.

Late last year when the CCNP changed I contacted Cisco Press about becoming a technical editor for any of their new books. I got on as the technical editor for the upcoming ISCW book, and managed to get roped into writing the questions that go in the back of the BCMSN book that just came out, the ISCW book that I edited, and the BSCI book that’s coming out. I’m almost done all but the last part.

I’ve also been busy helping b5media with systems administration and LAMP scaling, which has further pushed off my recert.

I’m happy to say I passed ISCW a couple of weeks ago. I think the book that’s coming out is well written, and I owe my success on that exam to having spent so much time studying the manuscript as it was being written.

I hope to write BSCI fairly soon. I’ve been focusing my studying on IPv6, multicast, and SONA largely because those are the areas I am concentrating on for the practice questions. However I’ve also been working on OSPF and IS-IS because those are my weak spots.

I’ve also got a pile of Cisco Press books that I’d like to share my opinion on in the coming weeks. The new CCNP video mentor is quite good, and I just received the BSCI pocket reference. If you like O’Reilly’s Hacks or Cookbooks series, I think you’ll be happy with these references.

Content Copyright Sean Walberg

A couple of random notes on progress

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- I’m 6′ tall, so my armspan is about 6′. Great for measuring the length of cables
- One big pace is about a meter (or 3′)
- Every megabit per second of bandwidth will transfer about half a Gig of data per hour, at best.
- having a rough idea of the cost of a switch, GBICs, and installation, rough guesses for the cost of data circuits (operational and capital), internet bandwidth costs

Any others?

Content Copyright Sean Walberg

Rules of Thumb

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Press release: http://biz.yahoo.com/bw/060815/20060815005343.html?.v=1

Summary of the changes (from the prep centre)

642-821 BCRAN becomes 642-825 ISCW Implementing Secure Converged WANS:
Security, DSL and MPLS added

642-831 CIT becomes 642-845 ONT Optimized Converged Cisco Networks:
QoS and WAN added

642-801 BSCI becomes 642-901 BSCI Building Scalable Cisco Internetworks:
Routing Protocols at Campus Edge added

642-811 BCMSN becomes 642-812 BCMSN Building Cisco Multilayer Switched Networks:
Campus Switch Networks and Wireless LANs added

The BCRAN replacement looks the most interesting.

Content Copyright Sean Walberg

CCNP Updated

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On most switches with a hardware priority queue (egress expedite queue) like the 3550, it’s statically assigned to queue 4 (on switches with 4 queues). Some switches like the 4500s let you switch the queue, but generally it’s on silicon so you’re stuck. No problem.

However, on the 3560 it’s queue 1. Luckily the commands are different (wrr-queue vs srr-queue) but it’s not exactly obvious that the pq isn’t in the same place.

I haven’t checked the 3750 series, I suspect they’ll also be on queue 1.

Content Copyright Sean Walberg

Hardware priority queues on Catalyst switches

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QoS involves giving better treatment to some traffic at the expense of others. It’s not going to make any more data fit on the pipe, it just tries to make all the applications happy. Take for instance VoIP and FTP. VoIP needs only a bit of bandwidth (<100Kbit/sec for a G.711 call), but if there is jitter (variation in latency) the call suffers. FTP doesn't care about delay or latency, it'll take as much of the pipe as it can handle (or is constrained because of TCP windowing). Here, the goal of QoS would be to make sure the voice gets the jitter control it needs. If we added in another application such as a CRM tool, we might give bandwidth guarantees to it such that voice gets the priority treatment, CRM gets enough bandwidth to do what it needs, and FTP gets the rest. We could also limito FTP. Such are the decisions necessary when designing QoS policies.

There are many ways of doing QoS in IOS, but the currently favoured method uses the Modular QoS CLI (MQC). The three phases are

1. Classify the packet
2. Mark the packet
3. Apply a treatment (also known as Per Hop Behaviour (PHB)) to the packet

(Technically, I suppose marking could be a treatment, but it’s usually considered separately.) Here, I’ll cover the classification step.

Classification

Classification involves mapping a packet to a series of classes. In QoS design, we generally don’t make a class specific to an application, we make it specific to a treatment. When taking the Cisco QoS course, we were told to keep the number of classes to 6 or fewer.

Classification criteria depends on the hardware, some of the things that are available are:

• Access-lists
• Layer 3 QoS (DSCP values)
• Layer 2 QoS (CoS bits)
• NBAR

This is done through the class-map command. The syntax is

 Router(config)#class-map ?
   WORD       class-map name
   match-all  Logical-AND all matching statements under this classmap
   match-any  Logical-OR all matching statements under this classmap

This creates the class map, and puts you in class-map configuration mode. The match-all and match-any specify whether all the match conditions that you enter in class-map configuration mode are required, or only one. The default is all.

Once configuring the class-map, you have to match things:

Router(config-cmap)#match ?
  access-group         Access group
  any                  Any packets
  class-map            Class map
  cos                  IEEE 802.1Q/ISL class of service/user priority values
  destination-address  Destination address
  fr-de                Match on Frame-relay DE bit
  input-interface      Select an input interface to match
  ip                   IP specific values
  mpls                 Multi Protocol Label Switching specific values
  not                  Negate this match result
  protocol             Protocol
  qos-group            Qos-group
  source-address       Source address

An example of a class-map that matches voice traffic by looking for the DSCP tag in the IP header is:

class-map match-all voice-traffic
  match ip dscp 46

Layer 2 and 3 QoS Marking

It's inefficient for a router to figure out what a packet is based on layer 4-7 criteria. It is far better to have the packet marked at the edge of the network and have the network look at that marking. At layer 2 this is called the Class of Service (COS), at layer 3 this is called the Differentiated Services Code Point (DSCP).

COS bits are the p part of 802.1p/q, and as such, are only carried in trunked packets. Note that in a .1q trunk, the native vlan isn't tagged by default, so it can't carry the COS bits. Within the 802.1q header are two bytes. 12 bits of this forms the VLAN tag, and 3 bits are used for the 802.1p priority.

3 bits doesn't tell you much, and dealing with headers at layer 2 is a pain (since the headers get rewritten at every switch hop). The IP header also had 3 bits (called TOS), which was later expanded to 6 to form the DSCP value. DSCP is defined in RFC 2474, and tries to give more meaning to the value than simply a priority between 0 and 63. RFC 2474 actually defines a full byte for the DSCP header with the DSCP value taking the high order 6 bits and the two low order bits unused. RFC 3168 uses these values to implement Explicit Congestion Notification, sort of like BECN/FECN for IP.

Differentiated Services Field Codepoints is a good document on the suggested classifications, culled from various RFCs, with some of my comments:

Name		Space			Reference
----		-----			---------
CS0		000000			[RFC2474]   CS* is used for compatibility with the old TOS bits
CS1		001000			[RFC2474]   so only the top 3 bits are used
CS2		010000			[RFC2474]
CS3		011000			[RFC2474]
CS4		100000			[RFC2474]
CS5		101000			[RFC2474]
CS6		110000			[RFC2474]
CS7		111000			[RFC2474]
AF11		001010			[RFC2597]  Assured Forwarding classes
AF12		001100			[RFC2597]
AF13		001110			[RFC2597]
AF21		010010			[RFC2597]
AF22		010100			[RFC2597]
AF23		010110			[RFC2597]
AF31		011010			[RFC2597]
AF32		011100			[RFC2597]
AF33		011110			[RFC2597]
AF41		100010			[RFC2597]
AF42		100100			[RFC2597]
AF43		100110			[RFC2597]
EF PHB		101110			[RFC3246]  Expedited Forwarding, this should be priority queued ie for voice.

The CS tags are for compatibility with the older TOS. From RFC 2597, the definition of the AF class is:

The AF PHB group provides delivery of IP packets in four
independently forwarded AF classes. Within each AF class, an IP
packet can be assigned one of three different levels of drop
precedence.

The drop predence is tied to a QoS mechanism called Random Early Detection, which will be looked at in another article.

Though we're getting out of the topic of classification, DSCP values don't necessarily follow a strict order. For instance, I've seen documents suggesting that normal traffic be set with CS0, and defined "bad" traffic to have CS1.

That's about it for classifying traffic until I start doing some examples. Once you have built your class-maps, you tie them to a behaviour using policy-maps, and then assign those to interfaces using service-policies. All in a future article!

Content Copyright Sean Walberg

QoS classification in a nutshell

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