InterVLAN Routing

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InterVLAN Routing Comparison between InterVLAN Routing types

Author: Ashour Shamoun Course: 1DV447 Advanced LAN Technologies Title: InterVLAN Routing Date: January 13, 2014

Course: 1DV447 Advanced LAN Technologies Title: InterVLAN Routing

Author: Ashour Shamoun Date: January 13, 2014

Table of Contents Table of Contents ................................................................................................................................. 2 Topology .............................................................................................................................................. 3 Introduction .......................................................................................................................................... 4 Task ...................................................................................................................................................... 4 Explanation ...................................................................................................................................... 4 Netperf ......................................................................................................................................... 4 Ping .............................................................................................................................................. 4 Tests ..................................................................................................................................................... 5 Ping test ............................................................................................................................................ 5 Netperf test ....................................................................................................................................... 6 CPU load .......................................................................................................................................... 7 Configuration ....................................................................................................................................... 9 Reflection ........................................................................................................................................... 11 References .......................................................................................................................................... 12

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Course: 1DV447 Advanced LAN Technologies Title: InterVLAN Routing

Author: Ashour Shamoun Date: January 13, 2014

Topology

During the project task there was some specifications required of the environment for each individual member. After combining all the requirements the network topology shown above was used during the project. The only difference between my test environment and the common network topology is that R3 will not be used because I noticed that the routers have different hardware even though they are of the same model.

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Course: 1DV447 Advanced LAN Technologies Title: InterVLAN Routing

Author: Ashour Shamoun Date: January 13, 2014

Introduction Since Virtual LANs [1] works on layer-2 and are isolated from each other, frames can’t cross between different VLANs. There has to be some layer-3 packet routing between the layer-2 VLANs for connectivity. The packet transportation between VLANs is traditionally a routers function through either a physical or logical interface to each VLAN, but can also be made through a Multilayer switch and this is known as InterVLAN routing [2].

There are three types of InterVLAN routing. Packets can be routed by a router with physical connection to each VLAN, or it could be performed by a single link with multiple sub-interfaces between a switch and router with a trunk [3] carrying all VLANs. It can also be made by a MLS (Multilayer switch) or a layer-3 switch.

In all interVLAN routing types, frames from different VLAN has to be forwarded by packets on layer-3, but all methods use different protocols or technologies and has different advantages and disadvantages. My main purpose with the project task was to investigate and compare Traditional routing, Router-on-a-Stick and MLS routing. The focus was on network throughput, latency and CPU load of the hardware.

Task I wanted to know which InterVLAN routing method is most efficient and fastest. I also wanted to know how the different methods affect and utilize the hardware. I had some idea if how to do it but I changed my plans to have different routers for the tests, as it is shown in the topology, because I noticed that even though the routers are of the same model they have different hardware. Therefore, I did the tests on the same router as I reconfigured for both tests that involved a router. I also tried to use the same client machine and the same cables in my tests to exclude unpredictable impact. I also wanted to compare a router and a MLS to see which device has better performance in packet routing and to do that, I had to disable CEF to make the MLS route by RP (routing processor) and switch by SE (switch engine) instead of route packets on hardware which is faster, but this part was hard to accomplish duo to equipment limitation.

Explanation Netperf Netperf [4] is an application used for network throughput measurement through TCP, UDP etc.

Ping Ping [5] is a software tool that provides connectivity test between nodes on a network.

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Course: 1DV447 Advanced LAN Technologies Title: InterVLAN Routing

Author: Ashour Shamoun Date: January 13, 2014

Tests To meet my requirement I decided to design two tests and compare the end result. I checked the latency with ping to measure network latency with the various interVLAN routing types. The second test was with Netperf to check the throughput and CPU load. I also wanted to check the memory usage, but it appeared not so clear, since IOS doesn’t have good tool for that.

Ping test I measured the latency of the network with Ping. I did 9 tests for each interVLAN routing type. Every test is a set of 26 pings which gives me an accurate average value. With the command ping –w 5 –s 100 –I 0.5 11.0.1.130 I could modify the ping package to send pings every 0.2 milliseconds and will stop after 5 seconds. The first ping test has a default ICMP packet value of 64 bytes and last one has a maximum value which is just below 65535, which is the maximum IP packet size. I have to think of ICMP header which is 32 bytes and therefore I have to modify the command to not exceed the desired value.

The output shows statistics and I am interested in the average time to compare it with the other ping tests.

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Course: 1DV447 Advanced LAN Technologies

Author: Ashour Shamoun

Title: InterVLAN Routing

Date: January 13, 2014

The comparison test result for ping between different InterVLAN routing types is shown below. Router-on-a-Stick

Traditional Routing

MLS

Packet size

Latency

Packet size

Latency

Packet size

Latency

64 bytes

0.739 ms

64 bytes

0.678 ms

64 bytes

0.568 ms

128 bytes

0.784 ms

128 bytes

0.721 ms

128 bytes

0.583 ms

1024 bytes

1.406 ms

1024 bytes

1.383 ms

1024 bytes

0.654 ms

2048 bytes

2.030 ms

2048 bytes

2.007 ms

2048 bytes

1.463 ms

4096 bytes

2.249 ms

4096 bytes

2.253 ms

4096 bytes

1.703 ms

8192 bytes

3.328 ms

8192 bytes

3.082 ms

8192 bytes

2.977 ms

16384 bytes

4.231 ms

16384 bytes

4.218 ms

16384 bytes

4.650 ms

32768 bytes

7.024 ms

32768 bytes

6.890 ms

32768 bytes

8.468 ms

65500 bytes

12.750 ms

65500 bytes

12.033 ms

65500 bytes

16.039 ms

Netperf test For the throughput and CPU load tests I used Netperf. For measuring the network accurate I did 5 tests with 128 bytes and 5 with the default value which is 2048 bytes. I decided to do the tests with different size of packets to see if there will be some difference on CPU load of the devices. The command for the first test is netperf –H 11.0.2.130 –t TCP_STREAM -- -m 128 and the second is netperf –H 11.0.2.130.

The output shows a throughput of 94.09 Mbps and other statistics.

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Course: 1DV447 Advanced LAN Technologies Title: InterVLAN Routing

Author: Ashour Shamoun Date: January 13, 2014

CPU load While I did the Netperf test, I also checked the router for CPU load with the command show process cpu history. IOS shows a graph with percentage CPU usage in seconds for last 60 seconds, last 60 minutes or last 72 hours. Example of output of the command show process cpu history is shown below.

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Course: 1DV447 Advanced LAN Technologies

Author: Ashour Shamoun

Title: InterVLAN Routing

Date: January 13, 2014

The comparison test result from Netperf between different InterVLAN routing types is shown below. Router-on-a-Stick Packet size

CPU load

Bandwith

128 bytes

38 %

90.98

128 bytes

36 %

128 bytes

Packet size

CPU load

Bandwith

2048 bytes

39 %

90.99

89.11

2048 bytes

38 %

90.99

38 %

91.00

2048 bytes

39 %

90.96

128 bytes

38 %

90.98

2048 bytes

38 %

89.05

128 bytes

39 %

90.97

2048 bytes

39 %

90.99

CPU load

Bandwith

Packet size

CPU load

Bandwith

128 bytes

30 %

94.05

2048 bytes

31 %

94.04

128 bytes

30 %

94.05

2048 bytes

30 %

94.03

128 bytes

30 %

94.05

2048 bytes

30 %

94.05

128 bytes

30 %

94.06

2048 bytes

30 %

94.05

128 bytes

31 %

94.06

2048 bytes

30 %

94.05

CPU load

Bandwith

Packet size

CPU load

Bandwith

Traditional routing Packet size

MLS Packet size 128 bytes

9%

94.10

2048 bytes

8%

94.11

128 bytes

10 %

94.07

2048 bytes

9%

94.10

128 bytes

10 %

94.08

2048 bytes

10 %

94.07

128 bytes

9%

94.11

2048 bytes

9%

94.12

128 bytes

9%

94.10

2048 bytes

9%

94.12

Router-on-a-Stick showed slightly heavier work load with bigger packet size, otherwise I can’t see any remarkable difference

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Course: 1DV447 Advanced LAN Technologies Title: InterVLAN Routing

Author: Ashour Shamoun Date: January 13, 2014

Configuration All configuration such as ports that are not used, or some particular configuration used by group members and is not relevant for my investigation will be excluded in order to keep the report short and readable. R2 configured as router on a stick

! hostname R2 ! interface FastEthernet0/1 no ip address ! interface FastEthernet0/1.50 encapsulation dot1Q 50 ip address 11.0.0.1 255.255.255.128 ! interface FastEthernet0/1.51 encapsulation dot1Q 51 ip address 11.0.0.129 255.255.255.128 ! end

R2 configured as ! traditional routing hostname R2 ! interface FastEthernet0/0 ip address 11.0.1.129 255.255.255.128 ! interface FastEthernet0/1 ip address 11.0.1.1 255.255.255.128 ! end

S2

! hostname S2 ! spanning-tree mode mst ! interface FastEthernet0/2 switchport access vlan 10 switchport mode access ! interface FastEthernet0/3 no switchport ip address 11.0.2.1 255.255.255.128 ! interface FastEthernet0/4 no switchport ip address 11.0.2.129 255.255.255.128 ! end

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Course: 1DV447 Advanced LAN Technologies Title: InterVLAN Routing

S4

Author: Ashour Shamoun Date: January 13, 2014

! hostname S4 ! ! spanning-tree mode mst ! interface FastEthernet0/1 switchport mode trunk ! interface FastEthernet0/2 switchport access vlan 52 switchport mode access ! interface FastEthernet0/3 switchport access vlan 53 switchport mode access ! interface FastEthernet0/5 switchport access vlan 50 switchport mode access ! interface FastEthernet0/6 switchport access vlan 51 switchport mode access ! interface FastEthernet0/7 switchport access vlan 52 switchport mode access ! interface FastEthernet0/8 switchport access vlan 53 switchport mode access ! ! interface Vlan1 no ip address ! end

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Course: 1DV447 Advanced LAN Technologies

Author: Ashour Shamoun

Title: InterVLAN Routing

Date: January 13, 2014

Reflection The main reason I wanted to do the tests was to compare MLS and routers and to find out which method is most suitable for routing packets between VLANs. I already know that traditional routing with two physical interfaces has more benefits than Router-on-a-Stick, since the latter uses layer-2 encapsulation and gets higher overhead. I could almost predict the results showing that traditional routing has better stats than a Router on a Stick, but how a router will perform against MLS switch was a question that I wanted to answer.

Since Catalyst 3560 uses CEF, the CPU load was very low in comparison to a router because CEF uses two tables for routing packets on two OSI-layers and reduces overhead and delays. Therefore I wanted to disable CEF to make it route packets without FIB, but there was no support on the platform. I was disappointed to not do a layer-3 routing comparison between MLS and router as I wanted due to equipment limitations. I think that even with CEF disabled the MLS will have slightly better delay stats but with higher CPU load.

Maybe there is another way to do the comparison without CEF and that would be using many networks and fill the FIB table with entries, but I think that the switch’s memory will be full long before that happens.

Beside CPU load, the throughput was the same for Traditional routing and MLS. Router-on-a-Stick had slightly lower value even though I didn’t reach the maximum bandwidth of the link.

Something strange happened with the ping tests. In comparison to the routers, the MLS showed lower network latency stats at the beginning, but got higher stats after 8 kilobytes. I don’t know why the switch behaved like that, but I don’t think that it had to do with the switch at all. I used same client for pinging through the router in both tests and another one for MLS. I think it had to do with some limitations in either the client itself or VMware which caused delay due packet fragmentation.

My conclusion is that if a network is not heavily trafficked, a MLS is the most suitable device to route traffic between VLANs. This is not surprising considering why it was invented in the first place.

If I get the chance to do a similar test, I would like to do it with multiple networks and see how the devices behave with more routes and higher traffic. I should also say that my conclusions are solely based on my tests without considering other requirements of the network.

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Course: 1DV447 Advanced LAN Technologies Title: InterVLAN Routing

Author: Ashour Shamoun Date: January 13, 2014

References [1] D. Huckaby, "Virtual LANs" in CCNP Switch 642-813: Official Certification Guide, Indianapolis: Cisco Press, 2011, pp. 65-69. [2] D. Huckaby, "Multilayer Switching" in CCNP Switch 642-813: Official Certification Guide, Indianapolis: Cisco Press, 2011, pp. 218-223. [3] D. Huckaby, "VLAN Trunks" in CCNP Switch 642-813: Official Certification Guide, Indianapolis: Cisco Press, 2011, pp. 70-75. [4] Network Sorvery Inc. (2014. 01, 13). ICMP, Internet Control Message Protocol [Online]. Availabe: http://www.networksorcery.com/enp/protocol/icmp.htm#ICMP%20Header%20Checksum [5] Netperf Org. (2014. 01, 13). Using Netperf to Measure Bulk Data Transfer [Online]. Availabe: http://www.netperf.org/svn/netperf2/tags/netperf-2.6.0/doc/netperf.html#Using-Netperf-toMeasure-Bulk-Data-Transfer

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