delay [tens-of-us]
Sets the delay value (in tens of microseconds) for an interface, used by routing protocols like EIGRP to calculate metric.
delay [tens-of-us]When to Use This Command
- Adjust EIGRP metric on a slow WAN link to prefer an alternative path
- Influence routing path selection by increasing delay on a backup interface
- Simulate higher latency for testing routing protocol behavior
- Fine-tune EIGRP composite metric without changing bandwidth
Command Examples
Setting delay on a serial interface
Router(config-if)# delay 20000Router(config-if)# end
Router# show interfaces serial 0/0/0
Serial0/0/0 is up, line protocol is up
Hardware is HD64570
Internet address is 192.168.1.1/24
MTU 1500 bytes, BW 1544 Kbit/sec, DLY 20000 usec,
reliability 255/255, txload 1/255, rxload 1/255The 'delay 20000' command sets the delay to 20000 tens of microseconds (i.e., 200,000 microseconds). In the output, 'DLY 20000 usec' shows the configured delay in microseconds. This value is used by EIGRP in its metric calculation.
Verifying delay with show interface
Router# show interfaces gigabitethernet 0/1GigabitEthernet0/1 is up, line protocol is up
Hardware is CN Gigabit Ethernet, address is aabb.cc00.0201 (bia aabb.cc00.0201)
Internet address is 10.0.0.1/24
MTU 1500 bytes, BW 1000000 Kbit/sec, DLY 10 usec,
reliability 255/255, txload 1/255, rxload 1/255The default delay for GigabitEthernet is 10 microseconds (displayed as 'DLY 10 usec'). This is a low delay value, indicating a high-speed link. The delay is used by EIGRP; lower delay results in a better (lower) metric.
Understanding the Output
The 'show interfaces' output includes the 'DLY' field which shows the interface delay in microseconds. This value is a key component in EIGRP metric calculation (metric = bandwidth + delay). A lower delay value indicates a faster link and results in a lower (more preferred) EIGRP metric. The default delay varies by interface type (e.g., 10 usec for GigabitEthernet, 20000 usec for serial). When troubleshooting routing issues, verify that the delay values are consistent with expected path selection. If a path is not being preferred, check if the delay has been manually changed or if defaults are appropriate. The delay is also used by other routing protocols like OSPF for cost calculation on certain platforms, but primarily it's an EIGRP metric component.
CCNA Exam Tips
Remember that delay is configured in tens of microseconds, but 'show interfaces' displays it in microseconds (multiply by 10).
EIGRP metric formula: metric = (K1 * BW + K3 * DLY) * 256, with default K values K1=1, K3=1. Delay is the sum of delays along the path.
The 'delay' command does not affect actual interface latency; it only influences routing protocol metrics.
On CCNA exam, you may be asked to calculate EIGRP metric changes after modifying delay on an interface.
Common Mistakes
Confusing delay units: the command uses tens of microseconds, but output shows microseconds. Setting 'delay 100' results in 1000 microseconds displayed.
Forgetting that delay changes affect EIGRP metric only if the interface is participating in EIGRP; other protocols may ignore it.
Setting delay to an extremely high value (e.g., 4294967295) which can cause metric overflow or unexpected path selection.
Related Commands
bandwidth [kbps]
Sets the bandwidth value (in kbps) on an interface for routing protocol metric calculations and QoS, overriding the default detected bandwidth.
show interfaces
Displays detailed status and statistics for all interfaces or a specific interface, used to verify interface operational state, errors, and performance.
show ip eigrp topology
Displays the EIGRP topology table, showing all learned routes and their feasible successors, used to verify EIGRP convergence and path selection.
show ip route
Displays the current IP routing table on a Cisco router, used to verify routes, check next-hop addresses, and troubleshoot connectivity issues.
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