How to convert TOS / AF / DSCP / IP Precedence

How to convert AF to DSCP

Explanation:

Take the first (AF) number and multiply it by 8, take the second (AF) number and multiply it by 2, add both results.

Formula: 

(8*x) + (2*y)

Example:

AF31 = (8*3) + (2*1) = 26 = DSCP 26

How to convert TOS to DSCP/IP Precedence

Explanation:

TOS stands for Type of Service and it’s an 8 bit filed in the IP header, IP Precedence uses only the 3 leftmost bits while DSCP uses the 6 leftmost bits.

 

 

(Taken from http://bogpeople.com/networking/dscp.shtml)

In order to convert TOS to DSCP/IP Precedence all we have to do is translate from binary to decimal.

Example:

TOS 160 = for having TOS 160 we need to put “1” (binary 0 or 1) on the 7^th and 5^th bits which will result in 128 (2^7) and 32 (2^5) = 160

Now because IP Precedence uses only the 3 leftmost bits (7, 6 and 5) and only the 1^st (5) and the 3^rd (7) bits are “1” the result will be 5.

The same manner for DSCP but this time with 6 bits calculation, where only the 6^th and the 4^th bits are “1” the result will be 40

Another example:

TOS 96 = the 6^th and 5^th bits are “1”

IP Precedence = because in TOS the 6^th and 5^th bits are “1” in IP Precedence its 1^st and 2^nd bits which result in (2^2) + (2^1) = 2 + 1 = 3

DSCP = because in TOS the 6^th and 5^th bits are “1” in DSCP its 4^th and 5^th bits which result in (2^5) + (2^4) = 16 + 8 = 24

GLBP

GLBP (Gateway Load-Balance Protocol) - 

Allow FHRP and load-balance traffic for the local segment.

For each segment there is 1 AVG (Active Virtual Gateway) which responsible for determine who will be the AVF (Active Virtual Forwarder) and up to 4 AVF’s.

Here is the following lab I setup in GNS:

R1, R2 and R3 are configured as GLBP group 1 for R4 and R6, R4 and R6 configured with default route to 10.1.0.254.

R1 Configuration:

interface FastEthernet1/0  ip address 10.1.0.1 255.255.255.0  glbp 1 ip 10.1.0.254  glbp 1 priority 110  glbp 1 preempt  glbp 1 authentication md5 key-string cisco  duplex full  speed 100 end

R2 Configuration:

interface FastEthernet1/0  ip address 10.1.0.2 255.255.255.0  glbp 1 ip 10.1.0.254  glbp 1 priority 120  glbp 1 preempt  glbp 1 authentication md5 key-string cisco  duplex full  speed 100 end

R3 Configuration:

interface FastEthernet1/0  ip address 10.1.0.3 255.255.255.0  glbp 1 ip 10.1.0.254  glbp 1 priority 130  glbp 1 preempt  glbp 1 authentication md5 key-string cisco  glbp 1 load-balancing host-dependent  duplex full  speed 100 end

A little explanation on the above configuration:

glbp 1 ip is very similar to HSRP or VRRP virtual IP, it’s he layer 3 IP which hosts refer to.

glbp 1 priority decide which router will be the AVG, higher priority wins.

glbp 1 preempt and authentication – again similar to HSRP/VRRP, no need to explain

glbp 1 load-balancing determine the way the AVG will load the traffic between the AVF’s, there are 3 modes for this option:

Host-depended – the source of the MAC address determine the AVF, which provides persistency. This method is recommended for segment with no more then 20 hosts.

Round-robin – the default option, in equal cyclic manner load-balance between the AVF’s

Weighted - Load balance in proportion to forwarder weighting. The default weight for each AVF is 100 and can be configured with glbp 1 weighting and can be monitored by track objects.

Cisco switch Hulc LED process

While working on Cisco c2960-S I noticed a relative high CPU utilization from a process called: Hulc LED process. This process is responsible for port link detection.

Note the process utilization:

SW# sh processes cpu sorted 1min CPU utilization for five seconds: 20%/1%; one minute: 21%; five minutes: 20%  PID Runtime(ms)   Invoked      uSecs   5Sec   1Min   5Min TTY Process  138    46080263   8555487       5386 10.89% 10.69% 10.76%   0 Hulc LED Process  292       67117       343     195676  0.00%  1.33%  0.33%   0 hulc running con  107     3052131    402562       7581  1.09%  0.76%  0.74%   0 hpm counter proc    4     3291391    183587      17928  0.00%  0.58%  0.71%   0 Check heaps        193     1430354   3734026        383  0.39%  0.53%  0.54%   0 Spanning Tree     102        1275       506       2519  1.29%  0.52%  0.25%   1 SSH Process       207      787430    402585       1955  0.29%  0.29%  0.28%   0 PI MATM Aging Pr  147      859812     81139      10596  0.19%  0.19%  0.19%   0 HQM Stack Proces    8      718295      6766     106162  0.00%  0.13%  0.13%   0 Licensing Auto U  103      562016   5191334        108  0.09%  0.12%  0.14%   0 hpm main process   69      365493   1865819        195  0.09%  0.07%  0.09%   0 RedEarth Tx Mana  178       26413    136403        193  0.00%  0.06%  0.03%   0 IP Input           70      275384  17099996         16  0.00%  0.05%  0.05%   0 RedEarth Rx Mana  277      101138      4403      22970  0.00%  0.04%  0.02%   0 VLAN Manager       10      281585    819737        343  0.00%  0.03%  0.05%   0 ARP Input         167      126435     79293       1594  0.00%  0.03%  0.02%   0 CDP Protocol      148       89198    162239        549  0.00%  0.03%  0.00%   0 HRPC qos request   51      112753     81121       1389  0.09%  0.02%  0.00%   0 Compute load avg   90       79497  11382877          6  0.00%  0.02%  0.00%   0 HLFM address ret   38      137240      6864      19994  0.00%  0.02%  0.00%   0 Per-minute Jobs    64       73121  14914414          4  0.00%  0.02%  0.00%   0 Draught link sta  290       25395    184969        137  0.00%  0.01%  0.00%   0 LACP Protocol     130       78811   1986300         39  0.00%  0.01%  0.00%   0 Hulc Storm Contr   89       56164    402586        139  0.09%  0.00%  0.00%   0 HLFM aging proce  228       53656    405943        132  0.00%  0.00%  0.00%   0 Socket Timers     139       24168    297706         81  0.00%  0.00%  0.00%   0 HL3U bkgrd proce  233       25970    817312         31  0.00%  0.00%  0.00%   0 DHCPD Receive      88      142355  11363812         12  0.00%  0.00%  0.00%   0 HLFM address lea   61        8382   1609843          5  0.00%  0.00%  0.00%   0 HUSB Console      180        5492    788015          6  0.00%  0.00%  0.00%   0 IP ARP Track       94        4991    135310         36  0.00%  0.00%  0.00%   0 HVLAN main bkgrd

In order to solve this issue you will have to shut down (administratively shut) all ports which are not connected.

The result:

CPU utilization for five seconds: 8%/0%; one minute: 9%; five minutes: 8%  PID Runtime(ms)   Invoked      uSecs   5Sec   1Min   5Min TTY Process  107     3075484    405876       7577  0.69%  0.68%  0.65%   0 hpm counter proc  193     1449905   3757786        385  0.49%  0.49%  0.49%   0 Spanning Tree     102         883       263       3357  0.69%  0.44%  0.20%   1 SSH Process         4     3318268    185088      17928  0.00%  0.44%  0.64%   0 Check heaps       207      796688    405899       1962  0.29%  0.26%  0.27%   0 PI MATM Aging Pr  138    46115118   8634102       5341  0.09%  0.25%  0.22%   0 Hulc LED Process    8      724256      6822     106164  0.00%  0.19%  0.13%   0 Licensing Auto U  147      866823     81805      10596  0.19%  0.19%  0.19%   0 HQM Stack Proces  167      127960     80072       1598  0.09%  0.06%  0.01%   0 CDP Protocol      178       26818    138168        194  0.29%  0.06%  0.01%   0 IP Input           51      113897     81787       1392  0.09%  0.04%  0.01%   0 Compute load avg   10      283352    825517        343  0.00%  0.03%  0.04%   0 ARP Input          38      138421      6921      20000  0.00%  0.03%  0.00%   0 Per-minute Jobs   103      563737   5237463        107  0.00%  0.02%  0.02%   0 hpm main process   64       73760  15040205          4  0.00%  0.01%  0.00%   0 Draught link sta  148       89937    163573        549  0.00%  0.01%  0.00%   0 HRPC qos request   33       67699    473302        143  0.00%  0.01%  0.00%   0 Net Background     90       79862  11478315          6  0.00%  0.00%  0.00%   0 HLFM address ret   70      276251  17256414         16  0.00%  0.00%  0.00%   0 RedEarth Rx Mana  139       24327    300155         81  0.09%  0.00%  0.00%   0 HL3U bkgrd proce   37      197463    406062        486  0.00%  0.00%  0.00%   0 Per-Second Jobs

You can see that the CPU utilization has decreased significantly.