Cisco ASR 920 Series Aggregation Services Router Configuration Guide, Cisco IOS XE Release 3S
Bias-Free Language
The documentation set for this product strives to use bias-free language. For the purposes of this documentation set, bias-free is defined as language that does not imply discrimination based on age, disability, gender, racial identity, ethnic identity, sexual orientation, socioeconomic status, and intersectionality. Exceptions may be present in the documentation due to language that is hardcoded in the user interfaces of the product software, language used based on RFP documentation, or language that is used by a referenced third-party product. Learn more about how Cisco is using Inclusive Language.
The Cisco ASR 920 Series Router (ASR-920-20SZ-M, ASR-920-24SZ-IM, ASR-920-24SZ-M, and ASR-920-24TZ-M)
do not have a ZTP or Reset button.
Note
Routers running ZTP must be able to connect to a DHCP server and TFTP server, download the configuration template, and begin
operation, all at the press of a button.
Prerequisites for Using ZTP
The Cisco ASR 920 Series Router must be running Cisco IOS-XE Release 3.13.0S or later.
The interface connected to the TFTP server must be turned green.
DHCP server should be configured to ensure reachability to the TFTP server.
Ports that are licensed through port licensing are disabled during the ZTP process. It is highly recommended that you connect
to free ports that do not need a license to be enabled. For information on port licensing, see Licensing 1G and 10G Ports on the Cisco ASR 920 Series Router
.
Caution
Do not change the ROMMON configuration register to 0x0.
Restrictions for Using ZTP
ZTP is not supported on the LAN Management port—Gig0 on the router. ZTP is supported only on the Ethernet interfaces such
as 1—Gige, 10—Gige ports, and so on.
ZTP is not initialized if the ZTP button is pressed for more than eight seconds. In this case, the router goes through a
normal reload process.
ZTP is also not initialized when the router is already reloading or if the router is in ROMMON prompt.
When the ZTP process is initialized all previous logs in the buffer are cleared.
DHCP declines addresses when loading DHCP configuration through TFTP. It is strongly recommended to have only the CNS configuration
present on the configuration file to avoid tampering with the ZTP BDI.
ZTP is not initialized if bootflash has files named as 'router-confg'.
Information About
Using ZTP
Figure 1. Sample ZTP
Topology
On the Cisco ASR 920
Series Routers, ZTP is triggered under any of the following conditions:
A router without a start up configuration is powered on
ZTP button is pressed (applicable on Cisco ASR 920 Series Router variants where the ZTP button is present on the front panel)
or,
The writeerase and reload commands are executed (applicable on Cisco ASR 920 Series Router variants where the ZTP button is not present on the front panel)
Note
The Cisco ASR 920 Series Routers (ASR-920-12CZ-A, ASR-920-12CZ-D, ASR-920-4SZ-A, ASR-920-4SZ-D, ASR-920-10SZ-PD, ASR-920-8S4Z-PD,
ASR-920-12SZ-D and ASR-920-12SZ-A) have a ZTP button on the front panel.
The Cisco ASR 920 Series Routers (ASR-920-20SZ-M, ASR-920-24SZ-IM, ASR-920-24SZ-M, and ASR-920-24TZ-M) do not have a ZTP or Reset button.
Router# write erase
System configuration has been modified. Save? [yes/no]: no
Router# reload
Note
If you type
yes at the
prompt, the system configuration is saved in the nvRAM and the ZTP process
terminates.
After the ZTP process
initializes, the following sequence is initiated:
The router detects the management VLAN and waits for any of the following data packets.
Broadcast (Gratuitous ARP)
ISIS hello packets
OSPF hello packets
IPv6 router advertisement packets
VRRP
Note
The operations center can initiate any of the above packets over the network to establish a connection to the DHCP server.
When the first packet on any VLAN is detected, the router initiates a DHCP session to a DHCP server over that VLAN.
After a DHCP session is established, the router must establish a connection with the TFTP server through DHCP option 43 or
DHCP option 150.
When connectivity to the TFTP server is established, the bootup process starts.
When the ZTP process
initiates, the Cisco ASR 920 Series Router creates an Ethernet flow point (EFP)
and associates a bridge domain interface (BDI) on the detected management VLAN.
The router creates the following configuration to establish a connection with the DHCP server and the TFTP server. The BDI
created for this purpose has description ZTP_BDI configured under the BDI interface.
Caution
Do not delete
ZTP_BDI.
Deleting this configuration results in loss of connectivity to the router and
the ZTP process terminates.
Note
Effective Cisco IOS-XE Release 3.14.0S, to stop the ZTP process when the ZTP button is accidentally pressed, use the ztpdisable command in global configuration mode. However, if you long press the ZTP button, (more than 8 sec) ZTP is still initialized
reload even though ZTP is disabled through the ztp disable command.
Example ZTP Configuration
Let us assume that GigabitEthernet0/0/1 is connected to the DHCP server and is used to connect to the TFTP server. VLAN ID
1000 is used as the management VLAN.
Router# show running-config int gi0/0/1
Building configuration...
Current configuration : 216 bytes
!
interface GigabitEthernet0/0/1
no ip address
media-type auto-select
no negotiation auto
service instance 12 ethernet
encapsulation dot1q 1000
rewrite ingress tag pop 1 symmetric
bridge-domain 12
!
end
!
interface BDI12
description ZTP_BDI
ip address dhcp
end
Downloading the Initial Configuration
After the VLAN discovery process is completed, the configuration download process begins. The following sequence of events
is initiated.
The router sends DHCP discover requests on each Ethernet interface.
The DHCP server allocates and sends an IP address, TFTP address (if configured with option 150) and default router address
to the router.
If the TFTP option (150) is present, the router requests a bootstrap configuration that can be stored in any of the following
files: PID-<mac-address>, network-confg, router-confg, ciscortr.cfg, or cisconet.cfg.
DHCP Server
The following is a sample configuration to set up a Cisco router as a DHCP server:
ip dhcp excluded-address 30.30.1.6
ip dhcp excluded-address 30.30.1.20 30.30.1.255
!
ip dhcp pool mwrdhcp
network 30.30.1.0 255.255.255.0
option 150 ip 30.30.1.6
default-router 30.30.1.6
This configuration creates a DHCP pool of 30.30.1.x
addresses with 30.30.1.0 as the subnet start. The IP address of the DHCP server is 30.30.1.6. Option 150 specifies the TFTP
server address. In this case, the DHCP and TFTP server are the same.
The DHCP pool can allocate from 30.30.1.1 to 30.30.1.19 with the exception of 30.30.1.6, which is the DHCP server itself.
TFTP Server
The TFTP server stores the bootstrap configuration file.
The following is a sample configuration (network– confg file):
hostname test-router
!
{ncs router-specifc configuration content}
!
end
ZTP LED Behavior
On Cisco ASR 920 Series Routers (ASR-920-12CZ-A, ASR-920-12CZ-D, ASR-920-4SZ-A, ASR-920-4SZ-D, ASR-920-10SZ-PD, ASR-920-8S4Z-PD
ASR-920-12SZ-D and ASR-920-12SZ-A):
Process
PWR LED
STAT LED
Press ZTP button
Green
Blinking Amber
Loading image
Blinking Green/Red
OFF
Image loaded
Green
Green
ZTP process running
Green
Blinking Amber
ZTP process success and config-file download completes
Green
Green
ZTP process failure or aborted
Green
Red
On Cisco ASR 920 Series Routers (ASR-920-20SZ-M, ASR-920-24SZ-IM, ASR-920-24SZ-M, and ASR-920-24TZ-M), using the writeerase and reload commands:
Process
PWR LED
STAT LED
Loading image
Blinking Green/Red
OFF
Image loaded
Green
Green
ZTP process running
Green
Blinking Amber
Verifying the ZTP Configuration
To verify if the ZTP configuration is successful, use the following command:
Feedback