Network Bulls
www.networkbulls.com
Best Institute for CCNA CCNP CCSP CCIP CCIE Training in India
M-44, Old Dlf, Sector-14 Gurgaon, Haryana, India
Call: +91-9654672192
This section presents two trouble tickets based on Unified Communications issues. In the
first trouble ticket (that is, Trouble Ticket #9), a Cisco IP Phone is failing to register with
its Cisco Unified Communications Manager Express (UCME) router. Once that issue is resolved,
the second trouble ticket (that is, Trouble Ticket #10) addresses poor voice quality
on the network. In each of these trouble tickets, you are given sample show command
output and are then challenged to identify a resolution for the issue described.
Trouble Ticket #9
You receive the following trouble ticket:
A Cisco IP Phone with directory number 3333 (connected to interface Fast Ethernet
5/45 on switch SW2) is unable to register with router R1, which is configured as a
UCME call agent. This is a new installation and has never worked. Therefore, no baseline
data is available.
This trouble ticket references the topology shown in Figure 11-12.
Assume that you have already verified reachability between switch SW2 and router R1
and have decided to focus your efforts on the configuration of the Cisco Unified Communications
Manager Express router (that is, router R1). Example 11-9 shows the running
configuration for router R1.
S 1/0.2
.1
Lo 0
10.3.3.3/32
S 1/0.2
.1
DLCI = 182
DLCI = 811
S 1/0.1
.1
Lo 0
10.1.1.1/32
Lo 0
10.2.2.2/32
172.16.1.X/30
Fa 0/0
DLCI = 881
Fa 0/0
.1
.2
Fa 0/0
.11
FXS
1/0/0
FXS
1/0/1
R2
192.168.1.X/24
10.1.2.X/24
192.168.0.X/24
.11
Fa 0/1
172.16.2.X/30
S 1/0.1
.2
DLCI = 882
Fa 0/0
.22
10.1.3.X/30
Gig 0/8 Fa 5/46
Lo 0
10.4.4.4/32
S 1/0.2
.2
DLCI = 821
Gig 0/9 Fa 5/47
Fa 5/45
x3333
Gig 0/10 Fa 5/48
100 Mbps
10 Mbps
R1
BB2
BB1
R2 FRSW
x1111 x2222
SW1 SW2
S 1/0.1
.2
DLCI = 181
Figure 11-12 Trouble Ticket #9—Topology
Example 11-9 Running Configuration of Router R1
R1# show run
Building configuration...
...OUTPUT OMITTED...
hostname R1
!
ip cef
!
ip dhcp excluded-address 192.168.0.1 192.168.0.100
!
ip dhcp pool TSHOOT
network 192.168.1.0 255.255.255.0
option 150 ip 192.168.0.11
default-router 192.168.0.11
!
interface Loopback0
ip address 10.1.1.1 255.255.255.255
!
interface FastEthernet0/0
ip address 192.168.1.11 255.255.255.0
!
interface FastEthernet0/1
ip address 192.168.0.11 255.255.255.0
!
router ospf 1
network 0.0.0.0 255.255.255.255 area 0
!
voice-port 1/0/0
!
voice-port 1/0/1
!
dial-peer voice 1111 pots
destination-pattern 1111
port 1/0/0
!
dial-peer voice 2222 pots
destination-pattern 2222
port 1/0/1
!
telephony-service
max-ephones 5
max-dn 10
ip source-address 192.168.0.11 port 2000
create cnf-files version-stamp Jan 01 2002 00:00:00
max-conferences 4 gain -6
!
ephone-dn 1
number 1000
!
ephone 1
mac-address 0008.A3D1.FBC4
button 1:1
!
...OUTPUT OMITTED...
Assume you have confirmed that the MAC address configured for ephone 1 is correct. Although
the TSHOOT curriculum does not cover the configuration of a UCME router,
Table 11-7 offers a reference for some of the commands used in Example 11-9.
Table 11-7 Sampling of Cisco UCME Configuration Commands
Command Description
telephony-service Global configuration mode command that enters the
configuration mode for setting up Cisco UCME parameters.
max-ephones number Telephony service configuration mode command that
specifies the maximum number of Ethernet phone directory
numbers supported on the UCME system.
(NOTE: The default is 0.)
max-dn number Telephony service configuration mode command that
specifies the maximum number of Ethernet phones
supported on the UCME system. (NOTE: The default
is 0.)
create cnf-files Telephony service configuration mode command that
creates .XML configuration files for configured
ephones.
ephone-dn tag Global configuration mode command that enters
ephone-dn configuration mode for a locally significant
ephone-dn tag.
number directory-number Ephone-dn configuration mode command that specifies
the directory number for an ephone-dn.
ephone tag Global configuration mode command that enters
ephone configuration mode for a locally significant
ephone tag.
continues
Table 11-7 Sampling of Cisco UCME Configuration Commands
Command Description
mac-addressMAC-address Ephone configuration mode command that specifies
the MAC address for an ephone. (NOTE: The MAC
address is entered in the following format:
xxxx.xxxx.xxxx.)
button button-number:ephone-dntag
Ephone configuration mode command that associates
a previously configured ephone-dn with a button
on the ephone.
ip source-address ip-address Global configuration mode command that specifies
the IP address on the UCME router used to send and
receive Skinny Client Control Protocol (SCCP) messages
when communicating with Cisco IP Phones.
dial-peer voice tag pots Global configuration mode command that creates a
Plain Old Telephone Service (POTS) dial peer.
destination-pattern pattern Dial peer configuration mode command that specifies
the pattern of a dial string to be matched.
(NOTE: Wildcards can be used.)
port port-identifier Dial peer configuration mode command that specifies
a voice port that a POTS dial peer references.
In an attempt to determine why the ephone registration is failing, you issue a debug
ephone command on router R1. However, no debug output is generated.
Therefore, you decide to look through the running configuration of router R1, as previously
presented in Example 11-9. On a separate sheet of paper, identify any misconfiguration
you find and how you would correct that misconfiguration.
Suggested Solution: Trouble Ticket #9
In the running configuration of router R1, you might have noticed that the DHCP pool
named THSOOT specified a network address space of 192.168.1.0 255.255.255.0. However,
if you examine the topology provided in Figure 11-12, you can see that the IP phone
(with directory number 3333) should be assigned an IP address in the 192.168.0.0
255.255.255.0 address space.
Example 11-10 shows the correction of this misconfiguration. Notice that after the configuration
is corrected, the ephone successfully registers.
Example 11-10 Correcting the DHCP Pool Misconfiguration on Router R1
R1# conf term
R1(config)# ip dhcp pool TSHOOT
R1(dhcp-config)# no network 192.168.1.0 255.255.255.0
R1(dhcp-config)# network 192.168.0.0 255.255.255.0
(Continued)
Trouble Ticket #10
Now that router R1 has been properly configured as a UCME router, the IP Phone (that is,
directory number 3333) and the analog phones (that is, directory numbers 1111 and 2222)
can call one another. Although the voice quality between these phones is fine on the
LAN, the following trouble ticket indicates quality issues when placing calls over the
Frame Relay WAN connections:
When placing calls across the Frame Relay WAN, users are complaining that the
voice quality is poor for calls originating on an analog phone, whereas the voice quality
is fine for calls originating on an IP phone.
This trouble ticket references the previous topology (that is, Figure 11-12). Because the
trouble ticket implies a QoS issue, you decide to investigate the configuration of router
R2 sitting at the WAN edge. Example 11-11 shows the output from a collection of show
commands.
Example 11-11 Verifying Configuration on Router R2
R1(dhcp-config)# end
R1#
*Mar 3 15:19:24.304: %IPPHONE-6-REG_ALARM: 22: Name=SEP0008A3D1FBC4 Load=7.1(2.0)
Last=Reset-Reset
*Mar 3 15:19:24.308: %IPPHONE-6-REGISTER: ephone-1:SEP0008A3D1FBC4
IP:192.168.0.101 Socket:1 DeviceType:Phone has registered.
R2# show class-map
Class Map match-any class-default (id 0)
Match any
Class Map match-all VOICE (id 1)
Match dscp ef (46)
R2# show policy-map
Policy Map TSHOOT
Class VOICE
Strict Priority
Bandwidth 256 (kbps) Burst 1600 (Bytes)
Class class-default
Flow based Fair Queueing
Bandwidth 0 (kbps) Max Threshold 64 (packets)
R2# show policy-map interface s1/0
Serial1/0
Service-policy output: TSHOOT
Class-map: VOICE (match-all)
0 packets, 0 bytes
5 minute offered rate 0 bps, drop rate 0 bps
Match: dscp ef (46)
Queueing
Strict Priority
Output Queue: Conversation 264
Bandwidth 64 (kbps) Burst 1600 (Bytes)
(pkts matched/bytes matched) 0/0
(total drops/bytes drops) 0/0
Class-map: class-default (match-any)
8 packets, 1010 bytes
5 minute offered rate 0 bps, drop rate 0 bps
Match: any
Queueing
Flow Based Fair Queueing
Maximum Number of Hashed Queues 256
(total queued/total drops/no-buffer drops) 0/0/0
Router R2’s configuration appears to be classifying voice traffic based on a packet’s DSCP
values. Specifically, if a packet is marked with a DSCP PHB value of EF (that is, Expedited
Forwarding, which has a decimal equivalent of 46), that packet is classified into the
VOICE class. Traffic in this class has access to as much as 256 kbps of bandwidth and is
given priority treatment.
Also provided as a reference, Example 11-12 shows the configuration of router R1.
Example 11-12 Verifying Configuration on Router R1
R1# show run
...OUTPUT OMITTED...
hostname R1
!
ip cef
!
ip dhcp excluded-address 192.168.0.1 192.168.0.100
!
ip dhcp pool TSHOOT
network 192.168.0.0 255.255.255.0
option 150 ip 192.168.0.11
default-router 192.168.0.11
interface Loopback0
ip address 10.1.1.1 255.255.255.255
interface FastEthernet0/0
ip address 192.168.1.11 255.255.255.0
!
interface FastEthernet0/1
ip address 192.168.0.11 255.255.255.0
!
router ospf 1
network 0.0.0.0 255.255.255.255 area 0
!
dial-peer voice 1111 pots
destination-pattern 1111
port 1/0/0
!
dial-peer voice 2222 pots
ip nat inside
destination-pattern 2222
port 1/0/1
!
telephony-service
max-ephones 5
max-dn 10
ip source-address 192.168.0.11 port 2000
create cnf-files version-stamp Jan 01 2002 00:00:00
max-conferences 4 gain -6
!
ephone-dn 1
number 1000
!
ephone 1
mac-address 0008.A3D1.FBC4
button 1:1
Based on the show command output, hypothesize how you could resolve the reported
quality issue. You can then compare your recommended solution with the following suggested
solution. Note that many possible solutions exist to solve this particular trouble
ticket.
Suggested Solution: Trouble Ticket #10
Because router R2 is giving priority treatment to traffic marked with a DSCP PHB value
of EF, you should ensure that all voice packets are being marked with that value. Cisco IP
Phones, by default, mark voice packets with an EF. However, by examining the configuration
of router R1 (that is, the router to which the two analog phones are attached), there
does not seem to be any configuration that marks voice packets sourced from the analog
voice ports with any DSCP value.
Therefore, router R1 should be configured to mark voice traffic with a DSCP PHB of EF.
Although you could do this manually, using more than one approach, this suggested solution
leverages the AutoQoS VoIP feature. By enabling AutoQoS VoIP on Router R1’s Fast
Ethernet 0/1 interface, voice packets will be automatically recognized (based on their use
of RTP). Example 11-13 illustrates the application and verification of the AutoQoS VoIP
feature to router R1.
Example 11-13 Applying and Verifying AutoQoS VoIP on Router R1
R1#conf term
R1(config)#int fa 0/1
R1(config-if)#auto qos voip
R1(config-if)#end
R1#show run
...OUTPUT OMITTED...
hostname R1
!
ip cef
!
ip dhcp excluded-address 192.168.0.1 192.168.0.100
!
ip dhcp pool TSHOOT
network 192.168.0.0 255.255.255.0
option 150 ip 192.168.0.11
default-router 192.168.0.11
!
class-map match-any AutoQoS-VoIP-Remark
match ip dscp ef
match ip dscp cs3
match ip dscp af31
class-map match-any AutoQoS-VoIP-Control-UnTrust
match access-group name AutoQoS-VoIP-Control
class-map match-any AutoQoS-VoIP-RTP-UnTrust
match protocol rtp audio
match access-group name AutoQoS-VoIP-RTCP
!
policy-map AutoQoS-Policy-UnTrust
class AutoQoS-VoIP-RTP-UnTrust
priority percent 70
set dscp ef
class AutoQoS-VoIP-Control-UnTrust
bandwidth percent 5
www.CareerCert.info
www.CareerCert.info
www - CareerCert - info
Chapter 11: IP Communications Troubleshooting 367
set dscp af31
class AutoQoS-VoIP-Remark
set dscp default
class class-default
fair-queue
!
interface Loopback0
ip address 10.1.1.1 255.255.255.255
!
interface FastEthernet0/0
ip address 192.168.1.11 255.255.255.0
!
interface FastEthernet0/1
ip address 192.168.0.11 255.255.255.0
auto qos voip
service-policy output AutoQoS-Policy-UnTrust
!
router ospf 1
network 0.0.0.0 255.255.255.255 area 0
!
ip access-list extended AutoQoS-VoIP-Control
permit tcp any any eq 1720
permit tcp any any range 11000 11999
permit udp any any eq 2427
permit tcp any any eq 2428
permit tcp any any range 2000 2002
permit udp any any eq 1719
permit udp any any eq 5060
ip access-list extended AutoQoS-VoIP-RTCP
permit udp any any range 16384 32767
!
rmon event 33333 log trap AutoQoS description “AutoQoS SNMP traps for Voice Drops”
owner AutoQoS
The highlighted commands in this example indicate the commands automatically entered
by the AutoQoS VoIP feature. After AutoQoS VoIP is applied, router R1 begins to mark
RTP audio packets (that is, voice packets) with a DSCP PHB of EF. Then, when those voice
packets reach router R2, router R2 is able to classify them into the VOICE class, which receives
priority treatment in being sent out over the Frame Relay WAN links, thus resolving
the reported issue.
No comments:
Post a Comment